ASTM F2703-21

Standard Test Method for Unsteady-State Heat Transfer Evaluation of Flame-Resistant Materials for Clothing with Burn Injury Prediction

SIGNIFICANCE AND USE
5.1 This test method is intended for the determination of a thermal performance estimate value of a material, a combination of materials, or a comparison of different materials used in flame-resistant clothing for workers exposed to combined convective and radiant thermal hazards.  
5.2 This test method evaluates a material’s heat transfer properties when exposed to a heat exposure at a constant value and specific duration. Air movement at the face of the specimen and around the calorimeter can affect the measured heat transferred due to forced convective heat losses. Minimizing air movement around the specimen and test apparatus will aid in the repeatability of the results.  
5.3 This test method accounts for the thermal energy stored in the exposed test specimen after the heat exposure has ceased. Higher values of thermal performance estimate ratings determined in this test associate to higher values of thermal (convective and radiative) energy protection against a predicted skin burn injury.  
5.4 This test method maintains the specimen in a static, horizontal position and does not involve movement except that resulting from the exposure.  
5.5 This test method specifies a standardized 84 ± 2 kW/m2 (2 ± 0.05 cal/cm2·s) exposure condition. Different exposure conditions have the potential to produce different results. Other exposure conditions representative of the expected hazard are allowed but shall be reported with the results along with a determination of the exposure energy level stability.  
5.6 This test method contains optional provisions for conducting certification testing against a prescribed thermal performance estimate value.
SCOPE
1.1 This test method measures the non-steady state heat transfer through flame-resistant materials for clothing subjected to a combined convective and radiant heat exposure.  
1.1.1 This test method is not applicable to materials that are not flame resistant.
Note 1: The determination of a material’s flame resistance shall be made prior to testing and done in accordance with the applicable performance or specification standard, or both, for the material’s end use.  
1.1.2 This test method accounts for the thermal energy contained in an exposed test specimen after the standardized combined convective and radiant heat exposure has ceased and is used to estimate performance to a predicted second-degree skin burn injury.  
1.2 This test method is used to measure and describe the response of materials, products, or assemblies to heat under controlled conditions, but does not by itself incorporate all factors required for fire hazard or fire risk assessment of the materials, products, or assemblies under actual fire conditions.  
1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversions to inch-pound or other units that are commonly used for thermal testing.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Oct-2021
• ICS: 13.340.10 - Protective clothing
• Technical Committee: F23 - Personal Protective Clothing and Equipment
• Drafting Committee: F23.80 - Flame and Thermal

Relations

• Refers: ASTM D1777-96(2019) - Standard Test Method for Thickness of Textile Materials
• Effective Date: 01-Jul-2019
• Refers: ASTM D3776/D3776M-09a(2017) - Standard Test Methods for Mass Per Unit Area (Weight) of Fabric
• Effective Date: 15-Jul-2017
• Refers: ASTM D123-17 - Standard Terminology Relating to Textiles
• Effective Date: 01-Mar-2017
• Refers: ASTM D123-15b - Standard Terminology Relating to Textiles
• Effective Date: 15-Sep-2015
• Refers: ASTM D123-15a - Standard Terminology Relating to Textiles
• Effective Date: 01-Sep-2015
• Refers: ASTM D1777-96(2015) - Standard Test Method for Thickness of Textile Materials
• Effective Date: 01-Jul-2015
• Refers: ASTM D123-15 - Standard Terminology Relating to Textiles
• Effective Date: 01-Apr-2015
• Refers: ASTM D3776/D3776M-09a(2013) - Standard Test Methods for Mass Per Unit Area (Weight) of Fabric
• Effective Date: 01-Jul-2013
• Refers: ASTM F1494-13 - Standard Terminology Relating to Protective Clothing
• Effective Date: 01-Jul-2013
• Refers: ASTM D123-13ae1 - Standard Terminology Relating to Textiles
• Effective Date: 15-Jun-2013
• Refers: ASTM D123-13a - Standard Terminology Relating to Textiles
• Effective Date: 15-Jun-2013
• Refers: ASTM D123-13 - Standard Terminology Relating to Textiles
• Effective Date: 15-May-2013
• Refers: ASTM D123-12e1 - Standard Terminology Relating to Textiles
• Effective Date: 01-Feb-2012
• Refers: ASTM D123-12 - Standard Terminology Relating to Textiles
• Effective Date: 01-Feb-2012
• Refers: ASTM D1777-96(2011)e1 - Standard Test Method for Thickness of Textile Materials
• Effective Date: 01-May-2011

Overview

ASTM F2703-21 is a standard test method developed by ASTM International for evaluating the unsteady-state heat transfer performance of flame-resistant materials used in protective clothing. This test method is crucial for predicting the likelihood of burn injury under exposure to combined convective and radiant heat sources, thereby supporting the safety and selection of materials for workers in high-risk environments. The method specifically applies to flame-resistant textiles, assessing their capacity to limit thermal energy transfer and providing a thermal performance estimate (TPE) related to predicted second-degree skin burns.

Key Topics

• Purpose: The standard provides a systematic approach to measure non-steady state heat transfer in flame-resistant materials, simulating real-world heat exposures that workers may encounter.
• Thermal Exposure Simulation: Materials are tested under a standardized combined heat source, typically at 84 ± 2 kW/m², to mirror hazardous working conditions involving both convective and radiant heat.
• Burn Injury Prediction: By capturing heat transfer data and comparing it to an empirical skin burn prediction curve, the method estimates the time and energy level at which a second-degree burn may occur.
• Post-Exposure Analysis: The method assesses both direct thermal transmission during exposure and residual energy stored within the textile after exposure ends.
• Repeatability & Controls: The approach minimizes air movement and mandates controlled environment settings to ensure consistent results.

Applications

ASTM F2703-21 is widely used in:

• Industrial Safety: Assisting manufacturers, safety professionals, and regulatory bodies in selecting appropriate flame-resistant clothing for at-risk workers, such as firefighters, utility line workers, petrochemical operators, and emergency responders.
• Quality Control: Providing objective, repeatable measurements for evaluating textile performance before products reach the market or are deployed in the field.
• Material Development: Guiding research and development into new or improved flame-resistant fabrics by enabling direct comparison of heat transfer characteristics.
• Certification Testing: Offering optional procedures to certify materials against prescribed thermal performance criteria, supporting regulatory compliance and end-user assurance.
• Comparative Assessment: Serving as a benchmark to compare different textile materials or constructions under identical heat exposure conditions.

Related Standards

When conducting tests according to ASTM F2703-21, the following related ASTM standards and procedures are often referenced:

• ASTM D123: Terminology Relating to Textiles, providing common definitions.
• ASTM D1776: Practice for Conditioning and Testing Textiles.
• ASTM D1777: Test Method for Thickness of Textile Materials.
• ASTM D3776/D3776M: Test Methods for Mass Per Unit Area (Weight) of Fabric.
• ASTM E457: Test Method for Measuring Heat-Transfer Rate Using a Thermal Capacitance (Slug) Calorimeter.
• ASTM F1494: Terminology Relating to Protective Clothing.

Practical Value

ASTM F2703-21 delivers critical insights for industries where protection from thermal hazards is essential. By determining the thermal performance estimate of flame-resistant textiles, organizations can:

• Select materials with proven efficacy against combined heat exposure.
• Enhance worker safety with clothing that resists ignition and limits burn injury.
• Comply with occupational health and safety regulations regarding protective clothing.
• Benchmark and improve the durability and performance of industrial workwear.

Through rigorous, scientifically-based testing, ASTM F2703-21 supports optimized safety practices and innovation in flame-resistant clothing for hazardous work environments.

Keywords: ASTM F2703-21, flame-resistant materials, unsteady-state heat transfer, protective clothing, burn injury prediction, thermal performance estimate, workplace safety, fire-resistant textiles.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F2703 − 21
Standard Test Method for
Unsteady-State Heat Transfer Evaluation of Flame-Resistant
Materials for Clothing with Burn Injury Prediction
This standard is issued under the fixed designation F2703; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This test method measures the non-steady state heat 2.1 ASTM Standards:
transfer through flame-resistant materials for clothing sub- D123Terminology Relating to Textiles
jected to a combined convective and radiant heat exposure. D1777Test Method for Thickness of Textile Materials
1.1.1 This test method is not applicable to materials that are D3776/D3776MTest Methods for Mass Per Unit Area
not flame resistant. (Weight) of Fabric
E457Test Method for Measuring Heat-Transfer Rate Using
NOTE 1—The determination of a material’s flame resistance shall be
a Thermal Capacitance (Slug) Calorimeter
made prior to testing and done in accordance with the applicable
F1494Terminology Relating to Protective Clothing
performance or specification standard, or both, for the material’s end use.
1.1.2 This test method accounts for the thermal energy
3. Terminology
contained in an exposed test specimen after the standardized
3.1 Definitions:
combinedconvectiveandradiantheatexposurehasceasedand
3.1.1 breakopen, n—in testing thermal protective materials,
is used to estimate performance to a predicted second-degree
amaterialresponseevidencedbytheformationofaholeinthe
skin burn injury.
test specimen during the thermal exposure that may result in
1.2 This test method is used to measure and describe the
the exposure energy in direct contact with the heat sensor.
response of materials, products, or assemblies to heat under
3.1.1.1 Discussion—The specimen is considered to exhibit
controlled conditions, but does not by itself incorporate all
breakopen when a hole is produced as a result of the thermal
factors required for fire hazard or fire risk assessment of the 2 2
exposure that is at least 3.2 cm (0.5 in. ) in area or at least
materials, products, or assemblies under actual fire conditions.
2.5cm (1.0 in.) in any dimension. Single threads across the
1.3 The values stated in SI units are to be regarded as opening or hole do not reduce the size of the hole for the
standard. The values given in parentheses are mathematical purposes of this test method.
conversions to inch-pound or other units that are commonly
3.1.2 charring, n—the formation of a carbonaceous residue
used for thermal testing.
as the result of pyrolysis or incomplete combustion.
1.4 This standard does not purport to address all of the
3.1.3 dripping,n—amaterialresponseevidencedbyflowing
safety concerns, if any, associated with its use. It is the
of the polymer.
responsibility of the user of this standard to establish appro-
3.1.4 embrittlement, n—the formation of a brittle residue as
priate safety, health, and environmental practices and deter-
a result of pyrolysis or incomplete combustion.
mine the applicability of regulatory limitations prior to use.
3.1.5 heat flux, n—the thermal intensity indicated by the
1.5 This international standard was developed in accor-
amountofenergytransmitteddividedbyareaandtime;kW/m
dance with internationally recognized principles on standard-
(cal/cm ·s).
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom- 3.1.6 ignition, n—the initiation of combustion.
mendations issued by the World Trade Organization Technical
3.1.7 melting, n—a material response evidenced by soften-
Barriers to Trade (TBT) Committee.
ing of the polymer.
3.1.8 response to heat exposure, n—in testing the resistance
to heat transfer of thermal protective materials, the observable
ThistestmethodisunderthejurisdictionofASTMCommitteeF23onPersonal
ProtectiveClothingandEquipmentandisthedirectresponsibilityofSubcommittee
F23.80 on Flame and Thermal. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Nov. 1, 2021. Published November 2021. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 2008. Last previous edition approved in 2013 as F2703–08 (2013). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/F2703-21. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2703 − 21
responseofthematerialtotheenergyexposureasindicatedby time-dependent cumulative heat response as measured by the
breakopen, melting, dripping, charring, embrittlement, calorimeter to a time-dependent, empirical predicted second-
shrinkage, sticking, and ignition. degree skin burn injury performance curve identified in
10.4.1.5, Eq 1).
3.1.9 sample test suite, n—any number of test specimens
used to derive a single thermal performance estimate value.
4.4 Observations of the thermal response of the specimen
3.1.9.1 Discussion—The determination of a single thermal
resulting from the exposure are optionally reported.
performance estimate value requires exposing a number of
specimens under varying exposure conditions so that the
5. Significance and Use
thermal energy stored in the sample after the heat source is
5.1 This test method is intended for the determination of a
removed is considered and accounted for when determining
thermal performance estimate value of a material, a combina-
performance against a burn injury prediction.
tionofmaterials,oracomparisonofdifferentmaterialsusedin
3.1.10 second-degree burn injury, n—in testing of thermal
flame-resistant clothing for workers exposed to combined
protective materials, reversible burn damage at the epidermis/
convective and radiant thermal hazards.
dermis interface in human tissue.
5.2 This test method evaluates a material’s heat transfer
3.1.11 shrinkage, n—a decrease in one or more dimensions
propertieswhenexposedtoaheatexposureataconstantvalue
of an object or material.
and specific duration. Air movement at the face of the
3.1.12 sticking, n—a material response evidenced by soft-
specimen and around the calorimeter can affect the measured
ening and adherence of the material to the surface of itself or
heattransferredduetoforcedconvectiveheatlosses.Minimiz-
another material.
ing air movement around the specimen and test apparatus will
3.1.13 thermal performance estimate (TPE), n—in testing of
aid in the repeatability of the results.
thermal protective materials, the cumulative amount of energy
5.3 This test method accounts for the thermal energy stored
identified by the intersection of a measured time-dependent
in the exposed test specimen after the heat exposure has
heat transfer response through a subject material to a time-
ceased. Higher values of thermal performance estimate ratings
dependent, empirical predicted second-degree skin burn injury
3 2 determined in this test associate to higher values of thermal
performance curve, expressed as a rating or value; J/cm
2 (convective and radiative) energy protection against a pre-
(cal/cm ).
dicted skin burn injury.
3.1.14 unsteady state heat transfer value, n—in testing of
5.4 This test method maintains the specimen in a static,
thermal protective materials, a quantity expressed as the
horizontalpositionanddoesnotinvolvemovementexceptthat
time-dependent difference between the incident and exiting
resulting from the exposure.
thermal energy values normal to and across two defined
parallel surfaces of an exposed thermal insulative material.
5.5 Thistestmethodspecifiesastandardized84 62kW/m
(2 6 0.05 cal/cm ·s) exposure condition. Different exposure
3.1.15 For the definitions of protective clothing terms used
in this method, refer to Terminology F1494, and for other conditionshavethepotentialtoproducedifferentresults.Other
exposure conditions representative of the expected hazard are
textile terms used in this method, refer to Terminology D123.
allowed but shall be reported with the results along with a
4. Summary of Test Method
determination of the exposure energy level stability.
4.1 Ahorizontally positioned test specimen is exposed to a
5.6 This test method contains optional provisions for con-
combined convective and radiant heat source with an exposure
ducting certification testing against a prescribed thermal per-
2 2
heat flux of 84 62kW/m (2 6 0.05 cal/cm ·s).
formance estimate value.
NOTE 2—Other exposure heat flux values are allowed, however,
different exposure conditions have the potential to produce different
6. Apparatus and Materials
results. The test facility shall verify the stability of other exposure levels
6.1 General Arrangement—The measurement apparatus
over the material’s exposure time interval (used to determine the thermal
performance estimate value) and include this in the test results report.
configuration consists of a combined convective and radiant
energy heat source, a water-cooled shutter for exposure
4.2 The unsteady-state transfer of heat through the test
control, a specimen and sensor support structure, a specimen
specimen is measured using a copper slug calorimeter. The
holder assembly, a copper calorimeter sensor assembly, and a
change in temperature versus time is used, along with the
data acquisition/analysis system. Automation of the apparatus
known thermophysical properties of copper, to determine the
for execution of the measurement procedure is allowed. The
respective thermal energy passed through the test specimen.
general arrangement of the test apparatus configuration is
4.3 A Thermal Performance Estimate value of the test
shown in Fig. 1.
specimen is determined iteratively as the intersection of the
6.2 Gas Supply—Propane (commercial grade or better) or
methane (technical grade or better).
Derivedfrom:Stoll,A.M.andChianta,M.A.,“MethodandRatingSystemfor
Evaluations of Thermal Protection,” Aerospace Medicine, Vol 40, 1969, pp.
6.3 Gas Flow Meter—Anygasflowmeterorrotometerwith
1232–1238 and Stoll,A. M. and Chianta, M.A., “HeatTransferThrough Fabrics as
rangetogiveaflowequivalentofatleast6L(0.21ft )/minair
Related to Thermal Injury,” Transactions – New York Academy of Sciences, Vol 33,
No. 7, 1971, pp. 649–670. at standard conditions.
F2703 − 21
NOTE 1—Note the exposure heat source incorporates two Meker burners and nine quartz infrared lamps.
FIG. 1 Apparatus Used to Measure Heat Transfer Performance of Textile Materials
6.4 Thermal Energy Source: spray paint with an absorptivity of 0.9 or greater. The painted
6.4.1 Two each, Meker or Fisher burners jetted for the sensor must be dried and cured, in accordance with the
selected fuel gas (propane or methane) with a 38 mm (1.5 in.) manufacturer’sinstructions,beforeuseandpresentauniformly
diameter top arranged so that the bodies (top section) do not appliedcoating(novisiblethickspotsorsurfaceirregularities).
obstruct the quartz lamps and their flame profiles overlap. In the absence of manufacturer’s instructions, an external heat
Dimension tolerances are 65%. source, for example, an external heat lamp, shall be used to
6.4.2 Nine 500W T3 translucent quartz infrared lamps, completelydriveoffanyremainingorganiccarriersinafreshly
connected to a variable electrical power controller, arranged as painted surface before use.
a linear array with 13 6 0.5 mm center-to-center spacing set
NOTE 3—Emissivity of painted calorimeters is discussed in theASTM
125 6 10 mm from the specimen surface.
Report, “ASTM Research Program on Electric Arc Test Method Devel-
6.4.2.1 Use of a water-cooled housing for the quartz infra-
opment to Evaluate Protective Clothing Fabric;ASTM F18.65.01 Testing
Group Report on Arc Testing Analysis of the F1959 Standard Test
red lamp bank is recommended. This helps to avoid heating
Method—Phase 1.”
adjacent mechanical components and to shield the operator
from the radiant energy. 6.5.2 The thermocouple wire bead is installed in the calo-
rimeter as shown in Fig. 2.
6.5 Thermal Sensor:
6.5.2.1 The thermocouple wire bead shall be bonded to the
6.5.1 Thetransmittedheatsensorisa4 60.05cmdiameter
5 copperdiskeithermechanicallyorbyusinghighmeltingpoint
circular copper slug calorimeter constructed from electrical
(HMP) solder.
gradecopperwithamassof18 60.05g(priortodrilling)with
(1)Amechanical bond shall be produced by mechanically
a single ANSI Type J (Fe/Cu-Ni) or ANSI Type K (Ni-Cr/Ni-
deforming the copper disk material (utilizing a copper filling
Al) thermocouple wire bead (0.254 mm wire diameter or finer,
slug as shown in Fig. 2) around the thermocouple bead.
equivalent to 30 AWG) installed as identified in 6.5.2 and
(2)A solder bond shall be produced by using a suitable
shown in Fig. 2. The sensor holder shall be constructed from
HMP solder with a melting temperature >280°C.
nonconductive heat-resistant material with a thermal conduc-
tivity value of ≤0.15 W/m·K, high temperature stability, and
NOTE 4—HMP solders consisting of 5%Sb-95%Pb (~307°C melting
point) and 5%Sb-93.5%Pb-1.5%Ag (;300°C melting point) have been
resistance to thermal shock. The board shall be nominally
found to be suitable. The 280°C temperature minimum identified above
1.3cm (0.5 in.) or greater in thickness. The sensor is held into
corresponds to the point where melting of the solder bond would be
the recess of the board using three straight pins, trimmed to a
experienced with an ~17 s exposure of an 84 kW/m heat flux to a
nominal length of 5 mm, by placing them equidistant around
prepared copper calorimeter with a surface area of 12.57 cm and a mass
the edge of the sensor so that the heads of the pins hold the of 18.0 g.Acareful soldering technique is required to avoid “cold” solder
joints (where the solder has not formed a suitable bond of the thermo-
sensor flush to the surface.
couple to the copper disk).
6.5.1.1 Paint the exposed surface of the copper slug calo-
rimeter with a thin coating of a flat black high-temperature
Zynolyte #635 from Aervoe Industries has been found suitable. Zynolyte is a
registered trademark of the Glidden Company.
4 7
A 500-Watt T3 120V AC quartz infrared heat lamp, product number 21651-1 Supporting data have been filed atASTM International Headquarters and may
from Philips Lighting Company has been used successfully in this application. beobtainedbyrequestingResearchReportRR:F18-1001.ContactASTMCustomer
See Test Method E457 for information regarding slug calorimeters. Service at [e-mail].
F2703 − 21
NOTE 1—Secure sensor into supporting insulation board with three sewing pins cut to a nominal 5 mm. All dimensional tolerances are 61%.
FIG. 2 Copper Calorimeter Sensor Detail
6.5.3 Weight the sensor board assembly so that the total of 60.75°C. It must be capable of making cold junction
massis1.0 60.01kgandthedownwardforceexhibitedbythe corrections and converting the millivolt signals from either the
copper slug sensor surface is uniform. Type J or K thermocouple to temperature (see NIST Mono-
graph 175 or ASTM MNL 12 Manual on the Use of
NOTE 5—Any system of weighting that provides a uniformly weighted
Thermocouples in Temperature Measurement).
sensorisallowed.Anauxiliarystainlesssteelplateaffixedtoorindividual
weightsplacedatthetopofthesensorassembly,orboth,havebeenfound
6.7 Solvents, alcohol or petroleum solvent for cleaning the
to be effective.
copper slug calorimeter.
6.6 Data Acquisition/Analysis System—A data acquisition/
6.8 Paint, flat black, spray type with an absorptivity value
analysis system is required that is capable of recording the
>0.90.
calorimeter temperature response, calculating the resulting
6.9 Specimen HolderAssembly—SeeFig.3.Threecomplete
thermal energy, and determining the test end point by compar-
assemblies are desirable for testing efficiency. Alteration is
ing the time-dependent thermal energy transfer reading to an
allowed to provide for mechanically restraining a specimen in
empirical performance curve.
the holder (see 10.3.2.1).
6.6.1 Thedataacquisitioncomponentshallhaveaminimum
sampling rate of four samples per second for temperatures to
250°C with a minimum resolution of 0.1°C and an accuracy Available from ASTM Headquarters.
F2703 − 21
FIG. 3 Details of Specimen Holder Construction, Specimen Holder Parts
NOTE 6—The upper specimen mounting plate is designed so that the
7.2 The specimen holder and calorimeter assembly become
coppercalorimeterassemblyfitsintothecentercutout.Anoptionalspacer
heated during testing. Use protective gloves when handling
component is also designed to fit into the center cutout with the copper
these hot objects.
calorimeter positioned on top of it. Tolerances for all dimensions are
61% to accommodate these arrangement requirements.
7.3 Usecarewhenthespecimenignitesorreleasescombus-
6.10 Shutter—A manual or computer-controlled shutter is tible gases. Remove the burner using gloves and allow the
usedtoblocktheheatfluxfromtheburner(placedbetweenthe sample to burn out, or smother it with a flat plate if necessary.
specimen holder and the burner). Water-cooling is recom-
7.4 Refer to manufacturer’s Material Safety Data Sheets
mended to minimize radiant heat transfer to other equipment
(MSDS) for information on handling, use, storage, and dis-
componentsandtopreventthermaldamagetotheshutteritself.
posal of materials used in this test method.
NOTE 7—Opening and closing times of the shutter are a source of
7.5 Refer to local codes for compliance on the installation
measurement variability. Accounting for these times, either manually or
and use of the selected fuel gas (propane or methane).
viacomputercontrol,intheexposuredurationhasbeenshowntoimprove
measurement precision.
8. Sampling and Specimen Preparation
7. Hazards
8.1 Laboratory Sample—Select a minimum of a 1.0 m
7.1 Perform the test in an appropriate exhaust hood that is
(1.2yd ) sample size from the material to be tested. Individual
designed to contain and carry away combustion products,
test specimens will be produced from this sample.
smoke, and fumes. Shield the apparatus or turn off the hood
8.2 Laundering of Laboratory Sample:
while running the test; turn the hood on to clear the fumes.
Maintain an adequate separation between the burner and 8.2.1 Forspecimenssubmittedwithoutexplicittestlaunder-
combustible materials. ing specifications, launder the laboratory sample for one wash
F2703 − 21
and dry cycle prior to conditioning. Use laundry conditions of 8.6 Determination of Test Specimens Average Surface
AATCC Test Method 135 (1, V, A, i). Density—Following the average thickness determination, use
the same three specimens to establish an average surface
8.2.1.1 Stitching the edges of the laboratory sample is
density (mass divided by surface area) following Test Method
allowed to minimize unraveling of the sample material.
D3776/D3776M.
8.2.1.2 Restoring test specimens to a flat condition by
pressing is allowed.
9. Preparation, Calibration, and Maintenance of
8.2.1.3 If an alternative laundry procedure is employed,
Apparatus
report the procedure used.
9.1 Remove the sensor assembly and any specimens from
8.2.2 For those materials that require cleaning other than
thespecimenholderandplacetheapparatusinitsmeasurement
laundering, follow the manufacturer’s recommended practice
position(sampleholderdirectlyovertheheatsource).Position
using one cleaning cycle followed by drying and note the
the two Meker or Fisher burners so that the center of each
procedure used in the test report.
burner head surface is separated by 125 6 10 mm, located 65
8.2.3 Record the procedure used in the test report for
6 10 mm beneath the specimen holder assembly opening, and
materials that are submitted with explicit laundering instruc-
subtending an approximate 45° angle from the vertical so that
tions.
the resulting flames converge at a point immediately beneath
8.2.4 Materials designated by the manufacturer not to be
the specimen.
laundered or cleaned shall be tested as received.
9.2 Heat Flux Calibration—Calibrating the dual burner/
8.3 Test Specimens—Cut the required test specimens from
quartz lamp heat source heat flux value is an iterative process
eachswatchinthelaboratorysample.Makeeachtestspecimen
that begins with the quartz infrared lamp assembly. After the
150by150 65mm(6by6 6 ⁄16in.)with(1)twoofthesides
lamp assembly heat flux is fixed, the burners are adjusted to
2 2
of the specimen parallel with the warp yarns in the woven
obtain an 84 6 2 kW/m (2.0 6 0.05 cal/cm ·s) value for
material samples; (2) the wales in knit material samples; or (3)
testing. Several calibration passes of both heat source compo-
the length of the material in batts or nonwovens. Do not cut
nents are typically required to establish the standard value for
samples closer than 10% of the material width from the edge;
testing within the specifications described below.
arrange the specimens diagonally across the sample swatch so
9.2.1 Set the output of the quartz infrared lamp assembly
as to obtain a representative sample of all yarns present.
afteraminimum15minwarm-upperiodto13 64kW/m (0.3
8.3.1 A minimum of five sample suites is required for 6 0.1 cal/cm ·s), as measured by an independent NIST
testing.The number of specimens in each suite will depend on traceable Schmidt-Boelter or Gardon type radiant heat flux
the measurement response. sensor, positioned in the same geometry as the copper calo-
rimeter sensor in the apparatus, using the lamp’s variable
NOTE 8—Experience has shown that the first sample suite typically
power control.
requires five to seven test specimens (especially if no prior knowledge of
the material’s response is known). The remaining four suites will on
NOTE 9—Fixing the NIST traceable Schmidt-Boelter or Gardon type
average require two to four test specimens each.
radiant heat flux sensor into an unused sensor supporting insulation board
(Fig. 2) has proven effective in calibration. Also note that the use of two
8.3.2 If the laboratory sample edges have been stitched to
properly adjusted Meker or Fisher burners and a quartz lamp bank (heat
reduce unraveling (see 8.2.1.1), test specimens shall be cut so 2
flux output set to 13 kW/m ) establishes an approximately 50% radiant,
they do not incorporate the stitching material.
50% convective heat flux at 84 kW/m for testing.
8.3.3 Three independent test specimens from those identi-
9.2.2 Burner Gas Supply—Reduce the pressure on the gas
fied above are required for determining average thickness and
supply to about 55 kPa (8 psig) to allow for proper flame
average surface density (see 8.5 and 8.6).
adjustment. Remove the Schmidt-Boelter or Gardon type
radiant heat flux sensor from the specimen holder (calibration
8.4 Conditioning—Condition each test specimen for at least
of the quartz lamp assembly is complete).
24hat21 62°C(70 65°F)and65 65%relativehumidity.
9.2.3 Leavethecalibratedquartzlampbankonandstartthe
The specimens shall be tested within 30 min of removal from
two burners at a low gas flow rate (low setting on the gas flow
the conditioning area.
meter/rotometer). Adjust the burner needle valves so that the
8.4.1 If any specimens removed from conditioning cannot
flames from each burner converge just below the center of the
betestedwithin30min,returnthemtotheconditioningareaor
specimen holder (hottest portion of the flames). Adjust the
seal them in polyethylene bags (or other material with low
combustion air control at the base of each burner so that the
water vapor permeability) until immediately prior to testing.
inner flame profile on the burner grids has clearly defined
8.4.2 Bagged specimens have a 4h storage limit and are
stable blue tips and the larger converging diffuse flames are
requiredtobetestedwithin20minafterremovalfromthebag.
blue.
8.4.3 Bagged specimens that exceed the 4h storage limit
9.2.4 Once the flame geometry in 9.2.3 is established, the
shall be removed from their bag and reconditioned in accor-
heat flux calibration is completed by increasing or decreasing
dance with 8.4 prior to testing.
the gas flow to the burners using the flowmeter/rotometer. Do
8.5 Determination of Test Specimens Average Thickness— notadjustthequartzlampassemblyonceithasbeencalibrated.
Determine the three specimens’average thickness identified in Minor burner needle valve and air flow adjustments are
8.3.3 following Test Method D1777. Save these specimens for allowed as required to maintain the converged flame profile
determining average surface density. characteristics.
F2703 − 21
9.2.5 Verify that the copper calorimeter sensor is at room holders to permit cooling between runs, or force cool with air
temperature. Ensure the sensor has a clean, black surface or water. Clean the holder with a non-aqueous solvent if it
without any accumulation of deposits. Otherwise, recondition becomes coated with tar, soot, or other decomposition prod-
the sensor surface as described in 9.3.2. Calibration shall not ucts.
proceed until the sensor temperature has stabilized (less than
1°C temperature change for a 1 min duration). 10. Procedure
9.2.6 With the heat source active, start the data acquisition
10.1 A minimum of five sample test suites is required for
system then place the sensor onto the specimen holder.
determination of a thermal performance estimate value. If
9.2.7 Exposethecoppercalorimetertotheheatsourceforat
additional specimen suites are taken from the laboratory
least 10 s.
sample and exposed, they shall be included in the determina-
9.2.8 Stop the data acquisition system and remove the
tion of the thermal resistance performance rating. Follow 10.6
sensor from the holder, placing it away from the apparatus
for optional certification testing.
where it is allowed to cool to room temperature.
10.1.1 Sample Test Suite—The determination of a single
sample test suite thermal performance estimate value requires
NOTE 10—Use protective gloves when handling the hot copper calo-
rimeter sensor.
multiple sample specimens and an iterative exposure tech-
NOTE11—Usingtheshuttertocontroltheheatfluxcalibrationexposure
nique.
in 9.2.6 – 9.2.8 is allowed but not required
10.2 Calibrate the Heat Source—Calibrate the system as
9.2.9 Calculatetheaverageexposureheatfluxvalueusinga
described in 9.1 and 9.2. Then carefully move the specimen
sampling interval that starts with the temperature measured at
holder assembly and burner away from each other to allow
time=0(datasampletakenjustasthesensorisplacedontothe
setting up the specimens and sensor in the apparatus for
sample holder) and ends with the temperature measured at
exposure.
exposure time = 10 s using the computational method identi-
10.3 Specimen Mounting—Single layer specimens are
fied in 11.1 (sensor response). This value is the measured heat
mountedeitherrestrained,torestrictheatshrinkage,orrelaxed,
flux.
to permit heat shrinkage. Choose restrained mounting to
9.2.10 Iftheheatfluxvaluedeterminedin9.2.9iswithinthe
2 2
evaluate barrier performance such as breakopen resistance.
specifications of 84 62kW/m (2.0 6 0.05 cal/cm ·s), the
Choose relaxed mounting for material shrinkage during expo-
system is considered calibrated. The actual measured value
sure. Multiple-layer samples are tested relaxed with the sensor
shall be recorded as the incident heat flux value and shall be
in contact with the back surface of the specimen, unless
usedforthedeterminationofthethermalperformanceestimate
otherwise specified.
valuein10.4.Iftheheatfluxvalueisoutsidethespecifications,
10.3.1 Optional Spacer—The optional 6.4 mm ( ⁄4 in.)
adjust the flow meter/rotometer in the direction required and
spacer, if used, is placed between the sensor assembly and the
repeat the calibration process (see 9.2.5 – 9.2.9).
back surface of the specimen. See Fig. 1 for a graphical
9.2.11 When the correct heat flux is achieved, note the flow
representation of the appropriate arrangement of the specimen
meter/rotometer reading (as well as all other settings for the
holder (with specimen), spacer, and sensor assembly.
specific apparatus configuration) as a guide for subsequent
10.3.2 Restrained Single Layer—Center the specimen on
adjustments.
the lower mounting plate with the surface that will be worn
9.3 Sensor Care:
next to the skin facing up and secure all four edges with
9.3.1 Initial Temperature—Cool the sensor after an expo-
pressure-sensitive tape of at least 12.7 mm (0.5 in.) width.
sure with a jet of air (or contact with a cold surface) to room
Attachoneedgeofthespecimentotheplateandthenattachthe
temperature, approximately 21°C (70°F), prior to positioning
opposite edge of the specimen, using slight tension to remove
the sensor onto the test specimen holder.Ameasurement shall
any sags or wrinkles. Do not pull enough to remove weave
not proceed until the sensor temperature has stabilized (less
crimp or distort a knit fabric or nonwoven structure. Similarly,
than 1°C temperature change for a 1 min duration).
attach the other two sides with slight tension. The securing
9.3.2 Surface Reconditioning—Wipe the sensor face with a
tapes will then contact the upper or inside face of the fabric.
nonabrasive material immediately after each exposure, while
Placetheuppermountingplateontopofthesecuredspecimen.
hot, to remove any decomposition products that condense on
10.3.2.1 A specimen holder with upper or lower, or both
the sensor since these could be a source of error. If a deposit
plate pins or other mechanical restraints is allowed for use in
collects and appears to be irregular or thicker than a thin layer
lieu of the pressure-sensitive tape.
of paint, the sensor surface requires reconditioning. Carefully
10.3.3 Relaxed Single Layer (heat shrinkage permitted)—
cleanthecooledsensorwithsolvent,makingcertainthereisno
Center the specimen on the lower mounting plate, with the
ignition source nearby. If bare copper is showing on the sensor
surface to be worn next to the skin facing up. Place the upper
surface, completely clean it to bare copper (remove any
mounting plate on top of the specimen. Do not restrain with
remaining paint on the surface) and repaint the copper sensor
tape or other mechanical means.
with a thin layer of flat black high-temperature spray paint
identifiedin6.5.1.1.Repeatthecalibrationprocess(see9.2.5–
9.2.9) with the resurfaced sensor before continuing.
An example of a lower mounting plate employing pins can be found in
9.4 Specimen Holder Care—Use dry specimen holders at
Canadian General Standards Board Standard CAN/CGSB-155.20-200 Workwear
ambienttemperaturefortestruns.Alternatewithseveralsetsof for Protection Against Hydrocarbon Flash Fire.
F2703 − 21
2 0.2901 2 0.2901
10.3.4 Multiple-Layer Samples—Place the surface of the J/cm 55.0204 3t cal/cm 51.1991 3t (1)
~ !
i i
material to be used as the outside of the garment face down on
wheret isthetimevalueinsecondsoftheelapsedtimesince
i
thelowermountingplate.Placethesubsequentlayersontopof
the initiation of the thermal exposure (shutter fully opened).
each other in the order used in the garment, with the surface to
Assignthemeasuredexposuretimevaluet equaltothetime
max
be worn toward the skin facing up. Place the upper mounting
where the measured cumulative heat exposure value of the test
plate on top of the layered specimen.
specimen intersects the empirical performance curve of Eq 1.
NOTE 12—Multiple-Layer Optional Spacer Use—The optional spacer This represents an approximate second-degree predicted burn
is typically used to simulate the average air layer between the inner
injury point for the continuous heating of the sample specimen
surface of a worn garment and the wearer. On some multilayer systems,
without accounting for heat remaining in the specimen.
use of the optional spacer can produce test conditions that exceed the
10.4.1.6 Allow the specimen holder and calo
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: F2703 − 08 (Reapproved 2013) F2703 − 21
Standard Test Method for
Unsteady-State Heat Transfer Evaluation of Flame Resistant
Flame-Resistant Materials for Clothing with Burn Injury
Prediction
This standard is issued under the fixed designation F2703; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method measures the non-steady state heat transfer through flame resistant flame-resistant materials for clothing
subjected to a combined convective and radiant heat exposure.
1.1.1 This test method is not applicable to materials that are not flame resistant.
NOTE 1—The determination of a material’s flame resistance shall be made prior to testing and done in accordance with the applicable performance or
specification standard, or both, for the material’s end-use.end use.
1.1.2 This test method accounts for the thermal energy contained in an exposed test specimen after the standardized combined
convective and radiant heat exposure has ceased and is used to estimate performance to a predicted second-degree skin burn injury.
1.2 This test method is used to measure and describe the response of materials, products, or assemblies to heat under controlled
conditions, but does not by itself incorporate all factors required for fire hazard or fire risk assessment of the materials, products,
or assemblies under actual fire conditions.
1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversions to
inch-pound or other units that are commonly used for thermal testing.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
This test method is under the jurisdiction of ASTM Committee F23 on Personal Protective Clothing and Equipment and is the direct responsibility of Subcommittee
F23.80 on Flame and Thermal.
Current edition approved June 1, 2013Nov. 1, 2021. Published June 2013November 2021. Originally approved in 2008. Last previous edition approved in 20082013 as
F2703 - 08.F2703 – 08 (2013). DOI: 10.1520/F2703-08R13.10.1520/F2703-21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2703 − 21
D123 Terminology Relating to Textiles
D1776 Practice for Conditioning and Testing Textiles
D1777 Test Method for Thickness of Textile Materials
D3776D3776/D3776M Test Methods for Mass Per Unit Area (Weight) of Fabric
E457 Test Method for Measuring Heat-Transfer Rate Using a Thermal Capacitance (Slug) Calorimeter
F1494 Terminology Relating to Protective Clothing
3. Terminology
3.1 Definitions:
3.1.1 breakopen, n—in testing thermal protective materials, a material response evidenced by the formation of a hole in the test
specimen during the thermal exposure that may result in the exposure energy in direct contact with the heat sensor.
3.1.1.1 Discussion—
The specimen is considered to exhibit breakopen when a hole is produced as a result of the thermal exposure that is at least 3.2
2 2
cm (0.5 in. ) in area or at least 2.5 cm 2.5 cm (1.0 in.) in any dimension. Single threads across the opening or hole do not reduce
the size of the hole for the purposes of this test method.
3.1.2 charring, n—the formation of a carbonaceous residue as the result of pyrolysis or incomplete combustion.
3.1.3 dripping, n—a material response evidenced by flowing of the polymer.
3.1.4 embrittlement, n—the formation of a brittle residue as a result of pyrolysis or incomplete combustion.
3.1.5 heat flux, n—the thermal intensity indicated by the amount of energy transmitted divided by area and time; kW/m
(cal/cm ·s).
3.1.6 ignition, n—the initiation of combustion.
3.1.7 melting, n—a material response evidenced by softening of the polymer.
3.1.8 response to heat exposure, n—in testing the resistance to heat transfer of thermal protective materials, the observable
response of the material to the energy exposure as indicated by breakopen, melting, dripping, charring, embrittlement, shrinkage,
sticking, and ignition.
3.1.9 sample test suite, n—any number of test specimens used to derive a single thermal performance estimate value.
3.1.9.1 Discussion—
The determination of a single thermal performance estimate value requires exposing a number of specimens under varying
exposure conditions so that the thermal energy stored in the sample after the heat source is removed is considered and accounted
for when determining performance against a burn injury prediction.
3.1.10 unsteady state heat transfer value, second-degree burn injury, n—in testing of thermal protective materials, a quantity
expressed as the time-dependent difference between the incident and exiting thermal energy values normal to and across two
defined parallel surfaces of an exposed thermal insulative material.reversible burn damage at the epidermis/dermis interface in
human tissue.
3.1.11 shrinkage, n—a decrease in one or more dimensions of an object or material.
3.1.12 sticking, n—a material response evidenced by softening and adherence of the material to the surface of itself or another
material.
F2703 − 21
3.1.13 thermal performance estimate (TPE), n—in testing of thermal protective materials, the cumulative amount of energy
identified by the intersection of a measured time-dependent heat transfer response through a subject material to a time-dependent,
3 2 2
empirical predicted second-degree skin burn injury performance curve, expressed as a rating or value; J/cm (cal/cm ).
3.1.14 response to heat exposure, unsteady state heat transfer value, n—in testing the resistance to heat transfer of thermal
protective materials, the observable response of the material to the energy exposure as indicated by break-open, melting, dripping,
charring, embrittlement, shrinkage, sticking, and ignition.a quantity expressed as the time-dependent difference between the
incident and exiting thermal energy values normal to and across two defined parallel surfaces of an exposed thermal insulative
material.
3.1.11 second-degree burn injury, n—in testing of thermal protective materials, reversible burn damage at the epidermis/dermis
interface in human tissue.
3.1.12 shrinkage, n—a decrease in one or more dimensions of an object or material.
3.1.13 sticking, n—a material response evidenced by softening and adherence of the material to the surface of itself or another
material.
3.1.14 sample test suite, n—any number of test specimens used to derive a single thermal performance estimate value.
3.1.14.1 Discussion—
the determination of a single thermal performance estimate value requires exposing a number of specimens under varying exposure
conditions so that the thermal energy stored in the sample after the heat source is removed is considered and accounted for when
determining performance against a burn injury prediction.
3.1.15 For the definitions of protective clothing terms used in this method, refer to Terminology F1494, and for other textile terms
used in this method, refer to Terminology D123.
4. Summary of Test Method
4.1 A horizontally positioned test specimen is exposed to a combined convective and radiant heat source with an exposure heat
2 2
flux of 84 6 2 kW/m (2 6 0.05 cal/cm s).·s).
NOTE 2—Other exposure heat flux values are allowed, however, different exposure conditions have the potential to produce different results. The test
facility shall verify the stability of other exposure levels over the material’s exposure time interval (used to determine the thermal performance estimate
value) and include this in the test results report.
4.2 The unsteady-state transfer of heat through the test specimen is measured using a copper slug calorimeter. The change in
temperature versus time is used, along with the known thermo-physicalthermophysical properties of copper, to determine the
respective thermal energy passed through the test specimen.
4.3 A Thermal Performance Estimate value of the test specimen is determined iteratively as the intersection of the time-dependent
cumulative heat response as measured by the calorimeter to a time-dependent, empirical predicted second-degree skin burn injury
performance curve identified in 10.4.1.5, Eq 1).
4.4 Observations of the thermal response of the specimen resulting from the exposure are optionally reported.
5. Significance and Use
5.1 This test method is intended for the determination of a thermal performance estimate value of a material, a combination of
materials, or a comparison of different materials used in flame resistant flame-resistant clothing for workers exposed to combined
convective and radiant thermal hazards.
Derived from: Stoll, A. M. and Chianta, M. A., “Method and Rating System for Evaluations of Thermal Protection,” Aerospace Medicine, Vol 40, 1969, pp. 1232–1238
and Stoll, A. M. and Chianta, M. A., “Heat Transfer throughThrough Fabrics as Related to Thermal Injury,” Transactions – New York Academy of Sciences, Vol 33, No. 7,
Nov. 1971, pp. 649–670.
F2703 − 21
NOTE 1—Note the exposure heat source incorporates two Meker burners and nine quartz infrared lamps.
FIG. 1 Apparatus Used to Measure Heat Transfer Performance of Textile Materials
5.2 This test method evaluates a material’s heat transfer properties when exposed to a heat exposure at a constant value and
specific duration. Air movement at the face of the specimen and around the calorimeter can affect the measured heat transferred
due to forced convective heat losses. Minimizing air movement around the specimen and test apparatus will aid in the repeatability
of the results.
5.3 This test method accounts for the thermal energy stored in the exposed test specimen after the heat exposure has ceased. Higher
values of Thermal Performance Estimatethermal performance estimate ratings determined in this test associate to higher values of
thermal (convective and radiative) energy protection against a predicted skin burn injury.
5.4 This test method maintains the specimen in a static, horizontal position and does not involve movement except that resulting
from the exposure.
2 2
5.5 This test method specifies a standardized 84 6 2 kW/m (2 6 0.05 cal/cm s)·s) exposure condition. Different exposure
conditions have the potential to produce different results. Other exposure conditions representative of the expected hazard are
allowed but shall be reported with the results along with a determination of the exposure energy level stability.
5.6 This test method contains optional provisions for conducting certification testing against a prescribed Thermal Performance
Estimatethermal performance estimate value.
6. Apparatus and Materials
6.1 General Arrangement—The measurement apparatus configuration consists of a combined convective and radiant energy heat
source, a water cooled water-cooled shutter for exposure control, a specimen and sensor support structure, a specimen holder
assembly, a copper calorimeter sensor assembly, and a data acquisition/analysis system. Automation of the apparatus for execution
of the measurement procedure is allowed. The general arrangement of the test apparatus configuration is shown in Fig. 1.
6.2 Gas Supply—Propane (commercial grade or better) or Methanemethane (technical grade or better).
6.3 Gas Flowmeter—Flow Meter—Any gas flowmeter flow meter or rotometer with range to give a flow equivalent of at least 6
L (0.21 ft )/min air at standard conditions.
F2703 − 21
6.4 Thermal Energy Source:
6.4.1 Two each, Meker or Fisher burners jetted for the selected fuel gas (propane or methane) with a 38 mm (1.5 in.) diameter
top arranged so that the bodies (top section) do not obstruct the quartz lamps and their flame profiles overlap. Dimension tolerances
are 65 %.
6.4.2 Nine 500W T3 translucent quartz infrared lamps, connected to a variable electrical power controller, arranged as a linear
array with 13 6 0.5 mm center-to-center spacing set 125 6 10 mm from the specimen surface.
6.4.2.1 Use of a water-cooled housing for the quartz infrared lamp bank is recommended. This helps to avoid heating adjacent
mechanical components and to shield the operator from the radiant energy.
6.5 Thermal Sensor:
6.5.1 The transmitted heat sensor is a 4 6 0.05 cm diameter circular copper slug calorimeter constructed from electrical grade
copper with a mass of 18 6 0.05 g (prior to drilling) with a single ANSI typeType J (Fe/Cu-Ni) or ANSI typeType K (Ni-Cr/Ni-Al)
thermocouple wire bead (0.254 mm wire diameter or finer—equivalent finer, equivalent to 30 AWG) installed as identified in 6.5.2
and shown in Fig. 2. The sensor holder shall be constructed from non-conductive heat resistant nonconductive heat-resistant
material with a thermal conductivity value of ≤ 0.15 ≤0.15 W/m·K, high temperature stability, and resistance to thermal shock. The
board shall be nominally 1.3 cm 1.3 cm (0.5 in.) or greater in thickness. The sensor is held into the recess of the board using three
straight pins, trimmed to a nominal length of 5 mm, by placing them equidistant around the edge of the sensor so that the heads
of the pins hold the sensor flush to the surface.
6.5.1.1 Paint the exposed surface of the copper slug calorimeter with a thin coating of a flat black high temperature
high-temperature spray paint with an absorptivity of 0.9 or greater. The painted sensor must be dried and cured, in accordance
with the manufacturersmanufacturer’s instructions, before use and present a uniformly applied coating (no visualvisible thick spots
or surface irregularities). In the absence of manufacturer’s instructions, an external heat source, for example, an external heat lamp,
shall be used to completely drive off any remaining organic carriers in a freshly painted surface before use.
NOTE 3—Emissivity of painted calorimeters is discussed in the ASTM Report, “ASTM Research Program on Electric Arc Test Method Development to
Evaluate Protective Clothing Fabric; ASTM F18.65.01 Testing Group Report on Arc Testing Analysis of the F1959 Standard Test Method—Phase 1.”
6.5.2 The thermocouple wire bead is installed in the calorimeter as shown in Fig. 2.
6.5.2.1 The thermocouple wire bead shall be bonded to the copper disk either mechanically or by using high melting point (HMP)
solder.
(1) A mechanical bond shall be produced by mechanically deforming the copper disk material (utilizing a copper filling slug
as shown in Fig. 2) around the thermocouple bead.
(2) A solder bond shall be produced by using a suitable HMP solder with a melting temperature >280°C.>280 °C.
NOTE 4—HMP solders consisting of 5 %Sb-95 %Pb (~307°C(~307 °C melting point) and 5 %Sb-93.5 %Pb-1.5 %Ag (;300°C(;300 °C melting point)
have been found to be suitable. The 280°C280 °C temperature minimum identified above corresponds to the point where melting of the solder bond would
2 2
be experienced with an ~17 seconds exposure of an 84 kW/m heat flux to a prepared copper calorimeter with a surface area of 12.57 cm and a mass
of 18.0 g. A careful soldering technique is required to avoid “cold” solder joints (where the solder has not formed a suitable bond of the thermocouple
to the copper disk).
6.5.3 Weight the sensor board assembly so that the total mass is 1.0 6 0.01 kg and the downward force exhibited by the copper
slug sensor surface is uniform.
NOTE 5—Any system of weighting that provides a uniformly weighted sensor is allowed. An auxiliary stainless steel plate affixed to or individual weights
A500 Watt T3 120VAC A 500-Watt T3 120V AC quartz infrared heat lamp, product number 21651-1 from Philips Lighting Company has been used successfully in this
application.
See Test Method E457 for information regarding slug calorimeters.
Zynolyte #635 from Aervoe Industries has been found suitable. Zynolyte is a registered trademark of the Glidden Company.
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:F18-1001. Contact ASTM Customer
Service at [e-mail].
F2703 − 21
NOTE 1—Secure sensor into supporting insulation board with three sewing pins cut to a nominal 5 mm. All dimensional tolerances are 6 1 %.61 %.
FIG. 2 Copper Calorimeter Sensor Detail
placed at the top of the sensor assembly, or both, have been found to be effective.
6.6 Data Acquisition/Analysis System—A data acquisition/analysis system is required that is capable of recording the calorimeter
temperature response, calculating the resulting thermal energy, and determining the test endpoint end point by comparing the
time-dependent thermal energy transfer reading to an empirical performance curve.
6.6.1 The data acquisition component shall have a minimum sampling rate of four samples per second for temperatures to
250°C250 °C with a minimum resolution of 0.1°C0.1 °C and an accuracy of 60.75°C.60.75 °C. It must be capable of making cold
junction corrections and converting the millivolt signals from either the typeType J or K thermocouple to temperature (see NIST
Monograph 175 or ASTM MNL 12 Manual on the Use of Thermocouples in Temperature MeasurementMeasurement).).
6.7 Solvents, alcohol or petroleum solvent for cleaning the copper slug calorimeter.
Available from ASTM Headquarters.
F2703 − 21
FIG. 3 Details of Specimen Holder Construction, Specimen Holder Parts
6.8 Paint, flat-black, flat black, spray type with an absorptivity value > 0.90.>0.90.
6.9 Specimen Holder Assembly—See Fig. 3. Three complete assemblies are desirable for testing efficiency. Alteration is allowed
to provide for mechanically restraining a specimen in the holder (see 10.3.2.1).
NOTE 6—The upper specimen mounting plate is designed so that the copper calorimeter assembly fits into the center cutout. An optional spacer component
is also designed to fit into the center cutout with the copper calorimeter positioned on top of it. Tolerances for all dimensions are 61 % to accommodate
these arrangement requirements.
6.10 Shutter—A manual or computer-controlled shutter is used to block the heat flux from the burner (placed between the
specimen holder and the burner). Water-cooling is recommended to minimize radiant heat transfer to other equipment components
and to prevent thermal damage to the shutter itself.
NOTE 7—Opening and closing times of the shutter are a source of measurement variability. Accounting for these times, either manually or via computer
control, in the exposure duration has been shown to improve measurement precision.
7. Hazards
7.1 Perform the test in an appropriate exhaust hood that is designed to contain and carry away combustion products, smoke, and
F2703 − 21
fumes. Shield the apparatus or turn off the hood while running the test; turn the hood on to clear the fumes. Maintain an adequate
separation between the burner and combustible materials.
7.2 The specimen holder and calorimeter assembly become heated during testing. Use protective gloves when handling these hot
objects.
7.3 Use care when the specimen ignites or releases combustible gases. Remove the burner using gloves and allow the sample to
burn out, or smother it with a flat plate if necessary.
7.4 Refer to manufacturer’s Material Safety Data Sheets (MSDS) for information on handling, use, storage, and disposal of
materials used in this test method.
7.5 Refer to local codes for compliance on the installation and use of the selected fuel gas (propane or methane).
8. Sampling and Specimen Preparation
2 2
8.1 Laboratory Sample—Select a minimum of a 1.0 m (1.2 yd(1.2 yd ) sample size from the material to be tested. Individual test
specimens will be produced from this sample.
8.2 Laundering of Laboratory Sample:
8.2.1 For specimens submitted without explicit test laundering specifications, launder the laboratory sample for one wash and dry
cycle prior to conditioning. Use laundry conditions of AATCC Test Method 135,135 (1, V, A, i).
8.2.1.1 Stitching the edges of the laboratory sample is allowed to minimize unraveling of the sample material.
8.2.1.2 Restoring test specimens to a flat condition by pressing is allowed.
8.2.1.3 If an alternative laundry procedure is employed, report the procedure used.
8.2.2 For those materials that require cleaning other than laundering, follow the manufacturer’s recommended practice using one
cleaning cycle followed by drying and note the procedure used in the test report.
8.2.3 Record the procedure used in the test report for materials that are submitted with explicit laundering instructions.
8.2.4 Materials designated by the manufacturer not to be laundered or cleaned shall be tested as received.
8.3 Test Specimens—Cut the required test specimens from each swatch in the laboratory sample. Make each test specimen 150 by
150 6 5 mm (6 by 6 6 ⁄16 in.) with (a)(1) two of the sides of the specimen parallel with the warp yarns in the woven material
samples; (b)(2) the wales in knit material samples; or (c)(3) the length of the material in batts or nonwovens. Do not cut samples
closer than 10 % of the material width from the edge; arrange the specimens diagonally across the sample swatch so as to obtain
a representative sample of all yarns present.
8.3.1 A minimum of five sample suites is required for testing. The number of specimens in each suite will depend on the
measurement response.
NOTE 8—Experience has shown that the first sample suite typically requires five to seven test specimens (especially if no prior knowledge of the material’s
response is known), theknown). The remaining four suites will on average require two to four test specimens each.
8.3.2 If the laboratory sample edges have been stitched to reduce unraveling (see 8.2.1.1), test specimens shall be cut so they do
not incorporate the stitching material.
8.3.3 Three independent test specimens from those identified above are required for determining average thickness and average
surface density (see 8.5 and 8.6).
F2703 − 21
8.4 Conditioning—Condition each test specimen for at least 24 h at 21 6 2°C2 °C (70 6 5°F)5 °F) and 65 6 5 % relative
humidity. The specimens shall be tested within 30 min of removal from the conditioning area.
8.4.1 If any specimens removed from conditioning cannot be tested within 30 min, return them to the conditioning area or seal
them in polyethylene bags (or other material with low water vapor permeability) until immediately prior to testing.
8.4.2 Bagged specimens have a four hour 4 h storage limit and are required to be tested within 20 min after removal from the bag.
8.4.3 Bagged specimens that exceed the four hour 4 h storage limit shall be removed from their bag and reconditioned in
accordance with 8.4 prior to testing.
8.5 Determination of Test Specimens Average Thickness—Determine the three specimens’ average thickness identified in 8.3.3
following ASTM Standard Test Method D1777. Save these specimens for determining average surface density.
8.6 Determination of Test Specimens Average Surface Density—Following the average thickness determination, use the same three
specimens to establish an average surface density (mass divided by surface area) following ASTM Standard Test Method
D3776D3776/D3776M.
9. Preparation, Calibration, and Maintenance of Apparatus
9.1 Remove the sensor assembly and any specimens from the specimen holder and place the apparatus in its measurement position
(sample holder directly over the heat source). Position the two Meker or Fisher burners so that the center of each burner head
surface is separated by 125 6 10 mm, located 65 6 10 mm beneath the specimen holder assembly opening, and subtending an
approximate 45-degree45° angle from the vertical so that the resulting flames converge at a point immediately beneath the
specimen.
9.2 Heat Flux Calibration—Calibrating the dual burner/quartz lamp heat source heat flux value is an iterative process that begins
with the quartz infrared lamp assembly. After the lamp assembly heat flux is fixed, the burners are adjusted to obtain an 84 6 2
2 2
kW/m (2.0 6 0.05 cal/cm s) ·s) value for testing. Several calibration passes of both heat source components are typically required
to establish the standard value for testing within the specifications described below.
9.2.1 Set the output of the quartz infrared lamp assembly after a minimum 15 min warm-up period to 13 6 4 kW/m (0.3 6 0.1
cal/cm s), ·s), as measured by an independent NIST traceable Schmidt-Boelter or Gardon type radiant heat flux sensor, positioned
in the same geometry as the copper calorimeter sensor in the apparatus, using the lamp’s variable power control.
NOTE 9—Fixing the NIST traceable Schmidt-Boelter or Gardon type radiant heat flux sensor into an unused sensor supporting insulation board (Fig. 2)
has proven effective in calibration. Also note that the use of two properly adjusted Meker or Fisher burners and a quartz lamp bank (heat flux output set
2 2
to 13 kW/m ) establishes an approximately 50 % radiant, 50 % convective heat flux at 84 kW/m for testing.
9.2.2 Burner Gas Supply—Reduce the pressure on the gas supply to about 55 kPa (8 psig) to allow for proper flame adjustment.
Remove the Schmidt-Boelter or Gardon type radiant heat flux sensor from the specimen holder (calibration of the quartz lamp
assembly is complete).
9.2.3 Leave the calibrated quartz lamp bank on and start the two burners at a low gas flow rate (low setting on the gas
flowmeter/rotometer). flow meter/rotometer). Adjust the burner needle valves so that the flames from each burner converge just
below the center of the specimen holder (hottest portion of the flames). Adjust the combustion air control at the base of each burner
so that the inner flame profile on the burner grids has clearly defined stable blue tips and the larger converging diffuse flames are
blue.
9.2.4 Once the flame geometry in 9.2.3 is established, the heat flux calibration is completed by increasing or decreasing the gas
flow to the burners using the flowmeter/rotometer. Do not adjust the quartz lamp assembly once it has been calibrated. Minor
burner needle valve and air flow adjustments are allowed as required to maintain the converged flame profile characteristics.
9.2.5 Verify that the copper calorimeter sensor is at room temperature. Ensure the sensor has a clean, black surface without any
accumulation of deposits. Otherwise, recondition the sensor surface as described in 9.3.2. Calibration shall not proceed until the
sensor temperature has stabilized (less than 1°C1 °C temperature change for a 1 min duration).
F2703 − 21
9.2.6 With the heat source active, start the data acquisition system then place the sensor onto the specimen holder.
9.2.7 Expose the copper calorimeter to the heat source for at least 10 s.
9.2.8 Stop the data acquisition system and remove the sensor from the holder, placing it away from the apparatus where it is
allowed to cool to room temperature.
NOTE 10—Use protective gloves when handling the hot copper calorimeter sensor.
NOTE 11—Using the shutter to control the heat flux calibration exposure in 9.2.6 – 9.2.8 is allowed but not required
9.2.9 Calculate the average exposure heat flux value using a sampling interval that starts with the temperature measured at time
= 0 (data sample taken just as the sensor is placed onto the sample holder) and ends with the temperature measured at exposure
time = 10 s using the computational method identified in 11.1 (Sensor(sensor response). This value is the measured heat flux.
2 2
9.2.10 If the heat flux value determined in 9.2.9 is within the specifications of 84 6 2 kW/m (2.0 6 0.05 cal/cm s),·s), the system
is considered calibrated. The actual measured value shall be recorded as the incident heat flux value and shall be used for the
determination of the Thermal Performance Estimatethermal performance estimate value in 10.4. If the heat flux value is outside
the specifications, adjust the flowmeter / rotometer flow meter/rotometer in the direction required and repeat the calibration process
(see 9.2.5 – 9.2.9).
9.2.11 When the correct heat flux is achieved, note the flowmeter / rotometer flow meter/rotometer reading (as well as all other
settings for the specific apparatus configuration) as a guide for subsequent adjustments.
9.3 Sensor Care:
9.3.1 Initial Temperature—Cool the sensor after an exposure with a jet of air (or contact with a cold surface) to room temperature,
approximately 21°C (70°F),21 °C (70 °F), prior to positioning the sensor onto the test specimen holder. A measurement shall not
proceed until the sensor temperature has stabilized (less than 1°C1 °C temperature change for a 1 min duration).
9.3.2 Surface Reconditioning—Wipe the sensor face with a nonabrasive material immediately after each exposure, while hot, to
remove any decomposition products that condense on the sensor since these could be a source of error. If a deposit collects and
appears to be irregular or thicker than a thin layer of paint, the sensor surface requires reconditioning. Carefully clean the cooled
sensor with solvent, making certain there is no ignition source nearby. If bare copper is showing on the sensor surface, completely
clean it to bare copper (remove any remaining paint on the surface) and repaint the copper sensor with a thin layer of flat black
high temperature high-temperature spray paint identified in 6.5.1.1. Repeat the calibration process (see 9.2.5 – 9.2.9) with the
resurfaced sensor before continuing.
9.4 Specimen Holder Care—Use dry specimen holders at ambient temperature for test runs. Alternate with several sets of holders
to permit cooling between runs, or force cool with air or water. Clean the holder with a non-aqueous solvent if it becomes coated
with tar, soot, or other decomposition products.
10. Procedure
10.1 A minimum of five sample test suites is required for determination of a Thermal Performance Estimatethermal performance
estimate value. If additional specimen suites are taken from the laboratory sample and exposed, they shall be included in the
determination of the thermal resistance performance rating. Follow 10.6 for optional certification testing.
10.1.1 Sample Test Suite—The determination of a single sample test suite Thermal Performance Estimatethermal performance
estimate value requires multiple sample specimens and an iterative exposure technique.
10.2 Calibrate the Heat Source—Calibrate the system as described in 9.1 and 9.29.1 and 9.2. Then carefully move the specimen
holder assembly and burner away from each other to allow setting up the specimens and sensor in the apparatus for exposure.
10.3 Specimen Mounting—Single layer specimens are mounted either restrained, to restrict heat shrinkage, or relaxed, to permit
heat shrinkage. Choose restrained mounting to evaluate barrier performance such as break-openbreakopen resistance. Choose
F2703 − 21
relaxed mounting for material shrinkage during exposure. Multiple-layer samples are tested relaxed with the sensor in contact with
the back surface of the specimen, unless otherwise specified.
10.3.1 Optional Spacer—The optional 6.4 mm ( ⁄4 in.) spacer, if used, is placed between the sensor assembly and the back surface
of the specimen. See Fig. 1 for a graphical representation of the appropriate arrangement of the specimen holder (with specimen),
spacer, and sensor assembly.
10.3.2 Restrained Single Layer—Center the specimen on the lower mounting plate with the surface that will be worn next to the
skin facing up and secure all four edges with pressure-sensitive tape of at least 12.7 mm (0.5 in.) width. Attach one edge of the
specimen to the plate and then attach the opposite edge of the specimen, using slight tension to remove any sags or wrinkles. Do
not pull enough to remove weave crimp or distort a knit fabric or nonwoven structure. Similarly, attach the other two sides with
slight tension. The securing tapes will then contact the upper or inside face of the fabric. Place the upper mounting plate on top
of the secured specimen.
10.3.2.1 A specimen holder with upper or lower, or both plate pins or other mechanical restraints is allowed for use in lieu of
the pressure-sensitive tape.
10.3.3 Relaxed Single Layer (heat shrinkage permitted)—Center the specimen on the lower mounting plate, with the surface to
be worn next to the skin facing up. Place the upper mounting plate on top of the specimen. Do not restrain with tape or other
mechanical means.
10.3.4 Multiple Layer Multiple-Layer Samples—Place the surface of the material to be used as the outside of the garment face
down on the lower mounting plate. Place the subsequent layers on top of each other in the order used in the garment, with the
surface to be worn toward the skin facing up. Place the upper mounting plate on top of the layered specimen.
NOTE 12—Multiple Layer Multiple-Layer Optional Spacer Use—The optional spacer is typically used to simulate the average air layer between the inner
surface of a worn garment and the wearer. On some multilayer systems, use of the optional spacer can produce test conditions that exceed the generally
accepted range of applicability of the literature derived literature-derived empirical exposure reference model (see 10.4.1.5, Eq 1) used in this test method.
This occurs when exposure times exceed ~60 s. The use of the spacer is not recommended for multilayer systems exceeding 60 s exposure times in this
configuration.
NOTE 13—The 60 second 60 s limit is a derived value based on an extrapolation of the curve identified in the cited literature reference (see Footnote 5).
10.4 Test Exposure—Follow the procedure outlined in 10.4.1 for samples with an unknown thermal performance estimate value.
Follow the procedure outlined in 10.4.2 for samples where the approximate thermal performance estimate value is known (for
example, repeats of sample test suites as identified in 10.1).
10.4.1 Test Exposure of Samples with Unknown Thermal Performance Estimate Values—A method of successive halving is
employed to determine the thermal performance estimate value.
10.4.1.1 Mount the specimen in the holder in accordance with 10.3.
10.4.1.2 Ensure that the sensor that has a clean, black surface without any accumulation of deposits otherwisedeposits; otherwise,
recondition the sensor surface as described in 9.3.2.
10.4.1.3 Place the copper calorimeter sensor assembly onto the specimen holder plate (with or without the spacer as selected in
10.3). The black copper slug shall always be facing downward towards the back of the specimen.
10.4.1.4 Place the shutter over the calibrated heat source to block the exposure radiant and convective thermal energy. Center the
combined sensor assembly/prepared specimen holder plate over the blocked heat source essentially matching the position used for
calibrating the sensor. Remove the shutter to expose the specimen to the heat source and simultaneously start the data acquisition
system (sensor data collection).
NOTE 14—Variations using a static sensor assembly and specimen holder (with shutter) with a movable heat source are allowed. Either sequence of events
can be manually functioned or computer controlled. Data acquisition initiation starts when the shutter completely unblocks the heat source.
An example of a lower mounting plate employing pins can be found in Canadian General Standards Board Standard CAN/CGSB-155.20-200 Workwear for Protection
Against Hydrocarbon Flash Fire.
F2703 − 21
NOTE 15—Use protective gloves when handling the hot shutter if a manual option is used.
NOTE 16—Opening and closing times of the shutter are a source of measurement variability. Accounting for these times, either manually or via computer
control, in the exposure duration has been shown to improve measurement precision.
10.4.1.5 Terminate the heat exposure to the specimen holder / calorimeter holder/calorimeter assembly by inserting the heat
blocking heat-blocking shutter and stop the data acquisition after the total accumulated thermal energy as measured by the
calorimeter (see 11.1) meets/exceeds the following empirical predicted second-degree skin burn injury performance curve criteria:
2 0.2901 2 0.2901
J/cm 5 5.0204 3t ~cal/cm 5 1.1991 3t ! (1)
i i
where t is the time value in seconds of the elapsed time since the initiation of the thermal exposure (shutter fully opened). Assign
i
the measured exposure time value t equal to the time where the measured cumulative heat exposure value of the test specimen
max
intersects the empirical performance curve of Eq 1. This represents an approximate second-degree predicted burn injury point for
the continuous heating of the sample specimen without accounting for heat remaining in the specimen.
10.4.1.6 Allow the specimen holder and calorimeter assembly to cool to room temperature before dissembling and removing the
exposed specimen.
NOTE 17—Use protective gloves when handling the hot shutter and specimen/copper calorimeter assembly.
10.4.1.7 Determine the exposure time trial value for the next iterative exposure by dividing t (determined in 10.4.1.5) by
max
two,two:
trial exposure time, t 5 t /2
trial max
10.4.1.8 Prepare another test specimen as outlined in 10.3.
10.4.1.9 Repeat 10.4.1.2 – 10.4.1.4 to initiate another exposure.
10.4.1.10 At t seconds, terminate the heat exposure to the specimen holder/calorimeter assembly by inserting the heat blocking
trial
heat-blocking shutter and separating the heat source and the specimen holder/sensor apparatus. Use care to minimize disturbing
the specimen holder/calorimeter assembly during the continuing data acquisition period.
NOTE 18—Avoid uncontrolled air flows and other sources of forced convection around the exposed specimen holder/sensor apparatus during data
acquisition to minimize measurement variation.
NOTE 19—Removing the flame burner gas energy by stopping the gas flow to the burners immediately after the initial heat exposure period has proven
effective to help terminate the heat source during the continuing data acquisition period.
10.4.1.11 Acquire calorimeter data for at least 30 secondss after terminating the heat exposure to the specimen and until the
thermal energy stored in the specimen has been released (into the calorimeter and environment). Data acquisition is terminated
when the cumulative energy as measured by the sensor begins to decrease. Acquisition times greater than 30 secondss after removal
are possible on heavy single and multilayer specimens.
10.4.1.12 From the measured calorimeter response, determine if a predicted second-degree burn injury occurred by comparing the
time-dependent cumulative heat response to the empirical second-degree burn injury performance curve, Eq 1 (see 11.1 for
determining sensor response).
(1) If a second-degree burn injury is not predicted (the measured heat response did not intersect the burn injury performance
curve), determine a new exposure time value that is half way halfway between the just completed t value and the higher previous
trial
exposure time value (for the first time through, the higher previous exposure time value will be t ). Assign t time to this value
max trial
and repeat 10.4.1.8 – 10.4.1.12.
(2) If a second-degree burn injury is predicted, determine a new exposure time value that is half way halfway between the just
completed t value and lower previous exposure time value (for the first time through, the lower previous exposure time value
trial
will be zero). Assign t time to this value and repeat 10.4.1.8 – 10.4.1.12.
trial
(3) If the difference between the current t and the previous t is ≤ 0.5 seconds, ≤0.5 s, then the thermal performance
trial trial
estimate value for this sample test suite is
thermal performance estimate value, J/cm 5
current t , seconds 3exposure heat flux value, kW/m /10
trial
F2703 − 21
thermal performance estimate value , cal / cm 5
~
current t , seconds 3exposure heat flux value, cal/cm s)
trial
thermal performance estimate value, J/cm 5
current t , seconds 3exposure heat flux value, kW/m /10
trial
thermal performance estimate value, cal/cm 5
~
current t , seconds 3exposure heat flux value, cal/cm s)
trial
(4) Subjective information observed during testing is optionally recorded with each exposure (see Appendix X1 and Appendix
X2Appendix X1 and Appendix X2).
10.4.2 Test Exposure of Samples with Approximately Known Thermal Performance Estimate Values—A method of successive
halving is employed to determine the thermal performance estimate value.
10.4.2.1 Assign the t value as
trial
t value,s 5 1.2 3approx thermal performance estimate value,
trial
~t value , s 5 1.2 3 approx thermal performance estimate value ,
trial
2 2
J/cm 310/radiant heat flux, kW/m
2 2
cal/cm /radiant heat flux, cal/cm s)
t value, s 5 1.2 3approx thermal performance estimate value,
trial
~t value, s 5 1.2 3approx thermal performance estimate value,
trial
2 2
J/cm 310/radiant heat flux, kW/m
2 2
cal/cm /radiant heat flux, cal/cm s)
and a previous t value as
trial
previous t value,s 5 0.8 3approx thermal performance estimate value,
trial
previous t value , s 5 0.8 3 approx thermal performance estimate value ,
~
trial
2 2
J/cm 310/radiant heat flux, kW/m
2 2
cal/cm /radiant heat flux, cal/cm s)
previous t value, s 5 0.8 3approx thermal performance estimate value,
trial
previous t value, s 5 0.8 3approx thermal performance estimate value,
~
trial
2 2
J/cm 310/radiant heat flux, kW/m
2 2
cal/cm /radiant heat flux, cal/cm s)
NOTE 20—withWith an approximately known thermal performance estimate value, the successive halving trial range can be reduced to conserve
specimens and speed the determination of a measured value for this sample suite. Narrowing the trial range to 620 % of the approximately known value
has demonstrated measurement convergence of a sample suite’s thermal performance estimate value in two to three exposure trials.
10.4.2.2 Prepare a test specimen as outlined in 10.3.
10.4.2.3 Initiate an exposure following 10.4.1.2 – 10.4.1.4.
10.4.2.4 At t seconds, terminate the thermal exposure by inserting the heat blocking heat-blocking shutter. Separate the
trial
specimen holder/calorimeter assembly from the heat source. Use care to minimize disturbing the specimen holder/calorimeter
assembly during data acquisition.
10.4.2.5 Acquire calorimeter data for at least 30 secondss after terminating the thermal exposure and until the heat stored in the
specimen has been released (into the calorimeter and environment). Data acquisition is stopped when the cumulative energy as
measured by the sensor begins to decrease. Acquisition times greater than 30 secondss after removal are possible on heavy single
and multi-layer specimens.
10.4.2.6 From the measured calorimeter response, determine if a predicted second-degree burn injury occurred by comparing the
time-dependent cumulative heat response to the empirical second-degree burn injury performance curve, Eq 1 (see 11.1 for
determining sensor response).
...