ASTM E1591-20

Standard Guide for Obtaining Data for Fire Growth Models

SIGNIFICANCE AND USE
4.1 This guide is intended primarily for users and developers of mathematical fire growth models. It is also useful for people conducting fire tests, making them aware of some important applications and uses for small-scale fire test results. The guide thus contributes to increased accuracy in fire growth model calculations, which depend greatly on the quality of the input data.  
4.2 The emphasis of this guide is on ignition, pyrolysis and flame spread models for solid materials.
SCOPE
1.1 This guide describes data required as input for mathematical fire growth models.  
1.2 Guidelines are presented on how the data can be obtained.  
1.3 The emphasis in this guide is on ignition, pyrolysis and flame spread models for solid materials.  
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.5 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.  
1.6 This fire standard cannot be used to provide quantitative measures.  
1.7 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-Mar-2020
• ICS: 13.220.01 - Protection against fire in general
• Technical Committee: E05 - Fire Standards
• Drafting Committee: E05.33 - Fire Safety Engineering

Relations

• Replaces: ASTM E1591-13 - Standard Guide for Obtaining Data for Fire Growth Models
• Effective Date: 01-Apr-2020
• Refers: ASTM E176-24 - Standard Terminology of Fire Standards
• Effective Date: 01-Jan-2024
• Refers: ASTM C835-06(2020) - Standard Test Method for Total Hemispherical Emittance of Surfaces up to 1400°C
• Effective Date: 01-Mar-2020
• Refers: ASTM E537-20 - Standard Test Method for Thermal Stability of Chemicals by Differential Scanning Calorimetry
• Effective Date: 01-Feb-2020
• Refers: ASTM D7309-19a - Standard Test Method for Determining Flammability Characteristics of Plastics and Other Solid Materials Using Microscale Combustion Calorimetry
• Effective Date: 01-Dec-2019
• Refers: ASTM E408-13(2019) - Standard Test Methods for Total Normal Emittance of Surfaces Using Inspection-Meter Techniques
• Effective Date: 01-Oct-2019
• Refers: ASTM E2058-19 - Standard Test Methods for Measurement of Material Flammability Using a Fire Propagation Apparatus (FPA)
• Effective Date: 01-Jul-2019
• Refers: ASTM D7309-19 - Standard Test Method for Determining Flammability Characteristics of Plastics and Other Solid Materials Using Microscale Combustion Calorimetry
• Effective Date: 01-May-2019
• Refers: ASTM E176-18a - Standard Terminology of Fire Standards
• Effective Date: 15-Dec-2018
• Refers: ASTM E1321-18 - Standard Test Method for Determining Material Ignition and Flame Spread Properties
• Effective Date: 01-Nov-2018
• Refers: ASTM E176-18 - Standard Terminology of Fire Standards
• Effective Date: 01-Mar-2018
• Refers: ASTM E1354-16a - Standard Test Method for Heat and Visible Smoke Release Rates for Materials and Products Using an Oxygen Consumption Calorimeter
• Effective Date: 01-May-2016
• Refers: ASTM E1354-16 - Standard Test Method for Heat and Visible Smoke Release Rates for Materials and Products Using an Oxygen Consumption Calorimeter
• Effective Date: 01-Feb-2016
• Refers: ASTM E2257-16 - Standard Test Method for Room Fire Test of Wall and Ceiling Materials and Assemblies
• Effective Date: 01-Feb-2016
• Refers: ASTM E1537-15 - Standard Test Method for Fire Testing of Upholstered Furniture
• Effective Date: 01-Nov-2015

Overview

ASTM E1591-20: Standard Guide for Obtaining Data for Fire Growth Models is an internationally recognized standard developed by ASTM International. This guide provides detailed recommendations for collecting and reporting data needed as input for mathematical fire growth models. Its primary focus is on ignition, pyrolysis, and flame spread calculations for solid materials, emphasizing the importance of data quality for the accuracy of fire modeling.

The standard is particularly geared toward researchers, model developers, and professionals conducting fire tests, supporting efforts to improve the predictive capabilities and reliability of fire growth simulations. All values in this guide are given in SI units, facilitating consistency and interoperability in global applications.

Key Topics

ASTM E1591-20 outlines essential parameters and recommended procedures for obtaining reliable fire test data. The key topics include:

• Combustion Efficiency: Guidelines for measuring effective vs. net heat of combustion using standardized apparatuses.
• Density: Recommendations on determining mass per unit volume for materials under varying thermal conditions.
• Emissivity: Methods for evaluating a material’s ability to emit thermal radiation, with related test apparatus.
• Flame Extinction Coefficient: Definitions and practical approaches for quantifying this parameter within fire modeling.
• Flame Spread Parameter: Use of standardized tests to obtain metrics regarding the rate and extent of flame propagation.
• Heat of Combustion, Gasification, and Pyrolysis: Procedures for measuring the energy characteristics of materials during various stages of burning and decomposition.
• Heat Release Rate: Importance of this measurement and related apparatus for different scales of fire tests.
• Ignition Temperature: Techniques for determining the critical temperature at which materials ignite.
• Mass Loss Rate: Recommended approaches for quantifying fuel consumption rates during fire exposure.
• Production Rate of Species: Measurement strategies for key combustion products affecting fire growth and smoke toxicity.
• Pyrolysis Temperature, Specific Heat, Thermal Conductivity, and Thermal Inertia: Guidelines for acquiring relevant thermophysical properties.

Applications

ASTM E1591-20 is a foundational document for applications where accurate fire growth modeling is critical, including:

• Fire Safety Engineering: Helps develop, calibrate, and validate mathematical fire growth models used for building safety analysis and risk assessments.
• Product Development: Useful for materials manufacturers and product designers seeking to understand or improve product response to fire exposure.
• Regulatory Compliance: Supports compliance with building codes and regulations, especially those requiring rigorous fire risk evaluations.
• Fire Testing Labs: Informs the design and execution of small-scale and large-scale fire tests, ensuring data relevancy for modeling.
• Insurance and Forensic Analysis: Assists in reconstructing fire scenarios and understanding material contributions to fire spread and severity.

Related Standards

Several ASTM standards are referenced or closely related to the implementation of ASTM E1591-20:

• ASTM E1354 - Heat and Visible Smoke Release Rates Using an Oxygen Consumption Calorimeter
• ASTM E1321 - Determining Material Ignition and Flame Spread Properties
• ASTM E1623 - Determination of Fire and Thermal Parameters of Materials Using Intermediate Scale Calorimeter
• ASTM D2395 - Density and Specific Gravity of Wood and Wood-Based Materials
• ASTM D3417, E537, E793 - Enthalpy, calorimetry, and thermal stability of materials
• ASTM E1537, E2257 - Furniture and room fire test standards

For comprehensive evaluations, users should refer to these related standards, ensuring that all data feeding into fire growth models are consistent, standardized, and credible.

With its structured approach, ASTM E1591-20 strengthens fire safety research, supports the accuracy of fire modeling in practice, and underpins regulatory and engineering decision-making related to fire hazards of materials and assemblies.

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: E1591 − 20 An American National Standard
Standard Guide for
Obtaining Data for Fire Growth Models
This standard is issued under the fixed designation E1591; 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 C1371Test Method for Determination of Emittance of
Materials Near Room Temperature Using Portable Emis-
1.1 This guide describes data required as input for math-
someters
ematical fire growth models.
D2395TestMethodsforDensityandSpecificGravity(Rela-
1.2 Guidelines are presented on how the data can be
tive Density) of Wood and Wood-Based Materials
obtained.
D3417Test Method for Enthalpies of Fusion and Crystalli-
1.3 The emphasis in this guide is on ignition, pyrolysis and zation of Polymers by Differential Scanning Calorimetry
flame spread models for solid materials. (DSC) (Withdrawn 2004)
D5865Test Method for Gross Calorific Value of Coal and
1.4 The values stated in SI units are to be regarded as
Coke
standard. No other units of measurement are included in this
D7309Test Method for Determining Flammability Charac-
standard.
teristics of Plastics and Other Solid Materials Using
1.5 This standard does not purport to address all of the
Microscale Combustion Calorimetry
safety concerns, if any, associated with its use. It is the
E176Terminology of Fire Standards
responsibility of the user of this standard to establish appro-
E408Test Methods for Total Normal Emittance of Surfaces
priate safety, health, and environmental practices and deter-
Using Inspection-Meter Techniques
mine the applicability of regulatory limitations prior to use.
E472Practice for Reporting Thermoanalytical Data (With-
1.6 Thisfirestandardcannotbeusedtoprovidequantitative
drawn 1995)
measures.
E537Test Method for Thermal Stability of Chemicals by
1.7 This international standard was developed in accor-
Differential Scanning Calorimetry
dance with internationally recognized principles on standard-
E793Test Method for Enthalpies of Fusion and Crystalliza-
ization established in the Decision on Principles for the
tion by Differential Scanning Calorimetry
Development of International Standards, Guides and Recom-
E906Test Method for Heat and Visible Smoke Release
mendations issued by the World Trade Organization Technical
Rates for Materials and Products Using a Thermopile
Barriers to Trade (TBT) Committee.
Method
E967Test Method for Temperature Calibration of Differen-
2. Referenced Documents
tial Scanning Calorimeters and Differential ThermalAna-
2.1 ASTM Standards:
lyzers
C177Test Method for Steady-State Heat Flux Measure-
E968Practice for Heat Flow Calibration of Differential
ments and Thermal Transmission Properties by Means of
Scanning Calorimeters
the Guarded-Hot-Plate Apparatus
E1321Test Method for Determining Material Ignition and
C518Test Method for Steady-State Thermal Transmission
Flame Spread Properties
Properties by Means of the Heat Flow Meter Apparatus
E1354Test Method for Heat and Visible Smoke Release
C835Test Method for Total Hemispherical Emittance of Rates for Materials and Products Using an Oxygen Con-
Surfaces up to 1400°C
sumption Calorimeter
E1537Test Method for Fire Testing of Upholstered Furni-
ture
ThisguideisunderthejurisdictionofASTMCommitteeE05onFireStandards
E1623Test Method for Determination of Fire and Thermal
andisthedirectresponsibilityofSubcommitteeE05.33onFireSafetyEngineering.
Parameters of Materials, Products, and Systems Using an
Current edition approved April 1, 2020. Published May 2020. Originally
Intermediate Scale Calorimeter (ICAL)
approved in 1994. Last previous edition approved in 2013 as E1591–13. DOI:
10.1520/E1591-20.
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 last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1591 − 20
E2058Test Methods for Measurement of Material Flamma- 6.1.3.2 Cone Calorimeter (Test Method E1354), ICAL Ap-
bility Using a Fire Propagation Apparatus (FPA) paratus (Test Method E1623), or the Fire Propagation Appa-
E2257Test Method for Room Fire Test of Wall and Ceiling ratus (Test Method E2058) for ∆h (see 6.6).
c,eff
Materials and Assemblies
6.2 Density:
6.2.1 Introduction:
3. Terminology
6.2.1.1 The density of a material is the mass of material per
3.1 Definitions—For definitions of terms appearing in this
unit volume. In fire models, density is usually expressed as
guide, refer to Terminology E176.
kg/m .
6.2.1.2 There are two reasons for density to change as a
4. Significance and Use
material is heated: volatile (flammable or nonflammable, or
4.1 This guide is intended primarily for users and develop-
both) may be lost and dimensional changes (expansion or
ers of mathematical fire growth models. It is also useful for
contraction) may occur. Although corrections for temperature
people conducting fire tests, making them aware of some
dependencecanbemade (1),manymodelsuseconstant(room)
important applications and uses for small-scale fire test results.
temperature values.
Theguidethuscontributestoincreasedaccuracyinfiregrowth
6.2.2 Procedures to Obtain Density:
model calculations, which depend greatly on the quality of the 6.2.2.1 The density of a material is determined by measur-
input data.
ing the mass and physical dimensions (volume) of a sample of
the material. There are detailed ASTM guidelines for certain
4.2 The emphasis of this guide is on ignition, pyrolysis and
types of building materials, for example, Test Methods D2395
flame spread models for solid materials.
for wood and wood-base materials.
6.2.2.2 When the temperature dependence of density is
5. Summary of Guide
sought, changes in mass with temperature can be determined
5.1 Thisguideprovidesacompilationofmaterialproperties
using thermogravimetric analysis and changes in dimensions
and other data that are needed as input for mathematical fire
with temperature using dilatometric analysis (1, 2).
growth models. For every input parameter, the guide includes
6.2.3 Apparatus to Be Used:
a detailed description and information on how it can be
6.2.3.1 Mass Balance (or equivalent).
obtained.
6.2.3.2 Caliper, Ruler (or equivalent).
5.2 The following input parameters are discussed: 6.1,
6.2.3.3 Dilatometric Apparatus .
combustion efficiency; 6.2, density; 6.3, emissivity; 6.4, flame
6.2.3.4 Thermogravimetric Analyzer .
extinction coefficient; 6.5, flame spread parameter; 6.6, heat of
6.3 Emissivity:
combustion; 6.7, heat of gasification; 6.8, heat of pyrolysis;
6.3.1 Introduction—The emissivity of a material is the ratio
6.9, heat release rate; 6.10, ignition temperature; 6.11, mass
of the power per unit area radiated from its surface to that
loss rate; 6.12, production rate of species; 6.13, pyrolysis
radiated from a black body at the same temperature. A
temperature; 6.14, specific heat; 6.15, thermal conductivity;
material’s emissivity represents its thermal radiative behavior
and 6.16, thermal inertia.
integrated over all wavelengths. Emissivity is a dimensionless
5.3 Some guidance is also provided on where to find values
quantity with an upper limit of unity for a black body.
for the various input parameters.
6.3.2 Procedures to Obtain Emissivity— Several standard
testmethodshavebeendevelopedtomeasuretheemissivityof
6. Data for Fire Growth Models
materials. A specimen of the material is usually placed in an
6.1 Combustion Effıciency:
evacuated chamber and heated (often with an electric current)
6.1.1 Introduction—The effective heat of combustion in to the temperature of interest. The power dissipated by the
fires is smaller than the net heat of combustion because of the
materialisdeterminedandequatedtotheradiativeheattransfer
incomplete combustion of fuel vapors. The combustion tothesurroundings.Theemissivityofthematerialiscomputed
efficiency, χ, accounts for incomplete combustion.
using this power and the Stefan-Boltzman equation.
6.1.2 Procedures to Obtain Combustion Effıciency—The
6.3.3 Apparatus to Be Used:
ratio between the effective heat of combustion and net heat of
6.3.3.1 Vacuum Emittance Test Apparatus (Test Method
combustion is the combustion efficiency. Thus,
C835).
6.3.3.2 Portable Emissometer (Test Methods C1371).
∆h
c,eff
χ 5 (1)
6.3.3.3 Inspection Meter (Test Methods E408).
∆h
net
6.4 Flame Extinction Coeffıcient:
where:
6.4.1 Introduction—The flame extinction coefficient interre-
∆h = effective heat of combustion, kJ/kg, and
c,eff
lates average radiation parameters such as emissivity, flame
∆h = net heat of combustion, kJ/kg.
c,net
intensity, and temperature over the entire spectrum of wave-
The combustion efficiency for most hydrocarbons ranges
lengths. It is used in the following equation to calculate the
from 0.4 to 0.9.
emissive power of a flame:
6.1.3 Apparatus to Be Used:
6.1.3.1 Test Method D5865 for ∆h (with adjustment for
c,net The boldface numbers in parentheses refer to a list of references at the end of
water vapor; see 6.6); and this standard.
E1591 − 20
˙ A 2kl self-consistent manner. Further details on consistent methods
E 5 AσT ~1 2 e ! (2)
f
to determine T and kρc can be found in 6.10 and 6.16,
ig
where:
respectively.
E = emissive power of the flame, W,
6.5.3 Apparatus to Be Used:
A = enveloping area of the flame, m ,
6.5.3.1 LIFT Apparatus (Test Method E1321).
−8 2 4
σ = Boltzman constant, 5.67·10 W/m ·K ,
6.6 Heat of Combustion:
T = flame temperature, K,
f
−1
6.6.1 Introduction—All combustion reactions generate
k = flame extinction coefficient, m , and
energy, which may be expressed as heat. The heat of combus-
l = path length, m.
tion is defined as the amount of heat generated when a unit
k is also called the absorption coefficient, absorption-
quantity of fuel is oxidized completely. SI units for heat of
emission coefficient, or effective emission coefficient.
combustion, ∆h , is kJ/kg.
c
6.4.2 Procedures to Obtain Flame Extinction Coeffıcient—
6.6.2 Procedures to Obtain Heat of Combustion:
The coefficient k can be estimated from measurement of the
6.6.2.1 Heats of combustion are measured by combustion
emissivity ε and path length l, assuming emissivity can be
bomb calorimetry.Aknown mass of fuel is burned completely
−kl
expressed as ε=1−e .
in an adiabatic apparatus containing pure oxygen.This method
yields the gross heat of combustion. The net heat of combus-
6.4.3 Apparatus to Be Used—There is no apparatus for
tion can be determined by subtracting the latent heat of
measuring the flame extinction coefficient. The extinction
evaporation (2.26 kJ/kg of water) from the gross heat of
coefficient can be determined by measuring all flame param-
combustion.
eters in the equation for Ė except k. Fire models include many
6.6.2.2 An effective heat of combustion can be obtained
of such empirical equations, but the documentation usually
from other tests that use oxygen calorimetry. For example, the
doesnotspecifywhattheparametersmeanandhowtheyareto
cone calorimeter (Test Method E1354) measures the mass loss
be determined. It must be stressed that the equation for Ė is
rateandheatreleaserate.Incompletecombustionmayoccurin
highly empirical. This makes it essential that the flame area,
this environment. The effective heat of combustion, ∆h ,is
c,eff
flame temperature, and extinction coefficient be determined in
the ratio between heat release rate and mass loss rate.
a self-consistent manner.
q˙
6.5 Flame Spread Parameter: ∆h 5 (4)
c,eff
m˙
6.5.1 Introduction:
where:
6.5.1.1 The opposed-flow (against the direction of the sur-
q˙ = heat release rate, kW, and
rounding flow or against gravity) flame spread rate over a
m˙ = mass loss rate of the sample, kg/s.
surface can be predicted via the equation originally developed
6.6.3 Apparatus to Be Used:
by deRis (3):
6.6.3.1 Oxygen Bomb Calorimetry (Test Method D5865).
φ
V 5 (3) 6.6.3.2 Cone Calorimeter (Test Method E1354).
p 2
kρc T 2 T
~ !
ig s
6.6.3.3 ICAL Apparatus (Test Method E1623).
where:
6.6.3.4 Furniture Calorimeter (Test Method E1537).
6.6.3.5 Microscale Combustion Calorimeter (Test Method
V = flame travel rate, m/s,
p
2 3
D7309).
φ = flame spread parameter, W /m ,
k = thermal conductivity, W/m·K,
6.7 Heat of Gasification:
ρ = density, kg/m ,
6.7.1 Introduction—The heat of gasification of a material is
c = heat capacity, J/kg·K,
equal to the net amount of heat that must be supplied through
T = surface temperature at ignition, K, and
ig
its exposed surface to convert a mass unit to gaseous volatiles.
T = surface temperature just prior to arrival of the flame
s
"
front, K.
q˙
net
∆h 5 (5)
g
m˙ "
6.5.1.2 The flame spread parameter, φ, for specific orienta-
where:
tionsandinstandardairenvironmentsisacharacteristicforthe
heattransferfromtheflametothefuelaheadoftheflamefront
q˙" = net heat flux into the material, kW/m , and
net
in the vicinity of the flame foot. It is a material property m˙ " = mass loss rate of the material, kg/m ·s.
2 3
∆h = heat of gasification, kJ/kg.
expressed in W /m .
g
6.5.2 Procedures to Obtain the Flame Spread Parameter—
6.7.2 Procedures to Obtain Heat of Gasification:
The flame spread parameter can be obtained from a correlation
6.7.2.1 For a flaming sample, the net heat flux conducted
of opposed-flow flame spread data, that is, flame spread rate
intothematerialisequaltothesumofradiationandconvection
overarangeofirradiancelevels(orsurfacetemperatures).The
from the flame and the external heat flux (from the radiant
test method described in Test Method E1321 was developed
heater in a small-scale test), minus the (radiant) heat losses
specifically to measure the flame spread parameter. It must be
from the surface.The flame flux and heat losses depend on the
stressed that the equation for V is highly empirical. This
surface temperature, which is very difficult to measure. The
p
makes it essential that V ,kρ c, and T be determined in a cone calorimeter (Test Method E1354) has been used, in
p ig
E1591 − 20
conjunction with surface temperature measurements, to deter- time-temperatureexposure.Heatisaddedtothesampleandan
mine ∆h for wood products and PMMA. inert reference compound so the two materials are maintained
g
at identical temperatures. The added heat is recorded and is
6.7.2.2 For some materials, the surface temperature is rea-
sonably constant and independent of exposure conditions. A assumed to equal the energy lost or gained as a result of the
endothermic or exothermic reaction. The sample environment
plot of (mean or peak) mass loss rates as a function of external
irradiance yields a fairly linear relationship for such materials. is purged with nitrogen or another inert gas when oxidation
reactions are not to be considered. DSC results are affected by
Values of ∆ h can then be estimated from the inverse of the
g
slope of the regression line through the data points. Tewarson such factors as particle size and heating rate. Because of these
factors, it can be argued that the DSC results for such small
and Petrella have used this technique to obtain ∆h values for
g
a wide range of plastics (4, 5). samples are not representative of the behavior of the material
in practice. DSC procedures are also used to measure the
6.7.2.3 Unfortunately, surface temperatures are not constant
for many materials, in particular charring materials and mate- enthalpy gain or loss associated with physical processes such
as vaporization and desorption, as well as the specific heat
rials with a high smoke yield. The method by Tewarson and
Petrella can still be used, but it yields results that have little capacity of a material.
6.8.2.2 The heat of pyrolysis (∆ h ) is generally considered
physical meaning. Various investigators have used the version
p
of the equation for ∆h and have obtained a time-dependent negativeforexothermicreactionsandpositiveforendothermic
g
reactions. DSC results are usually presented as a curve, with
heat of gasification curve instead of a single value (6-8)
the energy input on the ordinate with upward deflection
6.7.3 Apparatus to Be Used:
reflecting an exothermic reaction and time or temperature on
6.7.3.1 Cone Calorimeter (Test Method E1354).
theabscissaincreasingfromlefttoright.Standardpracticesfor
6.7.3.2 ICAL Apparatus (Test Method E1623).
reporting thermoanalytical data are given in Practice E472.
6.7.3.3 Fire Propagation Apparatus (Test Method E2058).
6.8.2.3 An alternative thermal analysis is differential ther-
6.8 Heat of Pyrolysis (Heat of Reaction):
mal analysis (DTA). The temperature difference between the
6.8.1 Introduction:
sample and the reference material is measured in DTA as a
6.8.1.1 Chemical reactions generally involve the generation
function of temperature. Quantitative results for the heat of
or absorption of energy. The heat of pyrolysis is the energy
pyrolysis can be calculated from DTAresults. Thermogravim-
emitted or lost during the pyrolysis or thermal degradation of
etry (TGA) can be used to measure the mass loss as a function
material. It is also defined as the difference between the
of temperature.
enthalpyofthevirginmaterialandtheenthalpyofthepyrolysis
6.8.2.4 Estimates for heat of pyrolysis have also been
products.Inthecalculationoftheheatofreaction,theproducts
calculated from other measurements. One alternative to mea-
are assumed to be at the pyrolysis temperature, and the virgin
suring the heat of reaction is to add the enthalpies of the
material is assumed to be at the ambient temperature. SI units
pyrolysis products and subtract them from the enthalpy of the
of the heat of pyrolysis are kJ/kg. It is sometimes expressed in
virgin material. Another procedure that has been used is to
kJ/m in models.
develop a transient heat balance model that has the heat of
6.8.1.2 Bench scale tests generally measure the heat of
pyrolysis as the unknown. The energy balance equation is
pyrolysisofasmallsampleexposedtowell-prescribedthermal
solved for the heat of pyrolysis based on experimentally
conditions. Heat of pyrolysis or the corresponding change in
obtained temperature profile data.
enthalpy is usually an input parameter in the energy balance
6.8.2.5 The methods mentioned above are not suitable for
equation for a solid material undergoing thermal degradation.
layered composite materials.
6.8.1.3 The heat of pyrolysis is generally found in models
6.8.3 Apparatus to Be Used:
that calculate the temperature profile within a solid material as
6.8.3.1 Several commercial instruments are available and
it is being heated. The internal energy generation term can be
are generally designed to perform other types of thermal
representedinseveraldifferentwaysdependingonmodel.One
analysisaswellasDSC.ThebasiccomponentsoftheDSCare
common way is to multiply the heat of pyrolysis Q (in kJ/kg)
thesamplecontainers,heatingunit,programmabletemperature
by the local rate of decomposition (in kg/m ·s) to obtain the
controller, inert reference material, and measuring and record-
energy generation term. An alternative is simply to use an
ing devices.
energy generation term dE/dt (in kW/m ).An alternative for Q
6.8.3.2 DSC procedures and apparatuses are discussed in
is to input the specific heat capacities and enthalpies of
Test Methods D3417, E537, and E793. Power-compensation
formation and have the computer program calculate the en-
DSC and heat-flux DSC are two types of apparatuses. Calibra-
thalpies and corresponding heat of pyrolysis Q. Some models
tion of DSC equipment is discussed in Practices E967 and
will not have a heat of pyrolysis term since the net energy
E968.
changeisassumedtobezero.Theenergygenerationtermmay
also include sensible energy as well as energy change due to 6.9 Heat Release Rate:
pyrolysis. 6.9.1 Introduction—A realistic calculation of the effects of
6.8.2 Procedures to Obtain Heat of Pyrolysis: fire requires knowledge of the burning rate. The burning rate
can be expressed as the mass generation rate of fuel volatile or
6.8.2.1 The most common experimental procedure to mea-
as a rate of heat release q˙. The units of heat release rate are W
sure the heat of pyrolysis is differential scanning calorimetry
or kW.
(DSC).Asmall quantity (a few mg) of sample is placed in the
apparatus. Thermal degradation is obtained using a specified 6.9.2 Procedures to Obtain Heat Release Rate:
E1591 − 20
6.9.2.1 The rate of heat release cannot be predicted from 6.10 Ignition Temperature:
basic measurements of material properties; it is a function of
6.10.1 Introduction:
the thermal environment, fuel volatilization, and efficiency of
6.10.1.1 Ignitionofasolidfuelisdefinedastheinitiationof
volatile combustion. The heat release rate and mass loss rate
flaming combustion in the gas phase. When a solid material is
are related by the following equation:
exposed to external heat, at some point it will begin to
pyrolyze. The fuel vapors mix with air in the boundary layer.
q˙ 5 m˙ χ∆h (6)
c,net
Shortly thereafter, the pyrolysis rate may be sufficient for the
where:
lowerflammabilitylimittobereached.Thismixturewillignite
∆h = net heat of combustion of the volatile, kJ/kg,
c,net
under certain conditions.
χ = combustion efficiency, and
6.10.1.2 Adistinction should be made between two types of
m˙ = mass loss rate of fuel, kg/s.
ignition:
6.9.2.2 The heat release rate can also be estimated by
(1)Piloted Ignition—Flaming combustion of the gas mix-
assuming that heat is generated by a reaction in which only
tureinitiatesatasmallpilotpresentinthegasphase.Thispilot
H O,CO ,andCOareproduced,andO isdepleted(9,chapter
may be a gas flame, an electric spark, or a glowing wire.
2 2 2
3). The heat release rate, q˙, can be calculated from the
Temperature is high enough locally around the pilot for the
following equations (10):
combustion reactions to start, provided the mixture is flam-
mable.
∆h
c,net
˙ "
q˙" 5 D (7)
O
(2)Unpiloted Ignition—If there is no pilot, the surface of
k
O
the solid must reach a sufficiently high temperature to trigger
and
the combustion reactions.
∆h ∆h 2 ∆ h
6.10.1.3 The prediction of when a solid fuel ignites if
c,net c,net CO
˙ " ˙ "
q˙" 5 G 1 G (8)
CO CO
k k
exposed to a certain heat flux is a very difficult problem. It
CO CO
includes consideration of heat and mass transfer, in both the
where:
solid and gas phases, and fluid flow and mixing in the gas
q˙" = heat release rate per unit area, kW/m ,
phase. Many investigators have assumed a critical surface
∆h = net heat of complete combustion of the material,
c,net
temperature criterion for ignition in order to simplify the
kJ/kg,
problemwhilemaintainanacceptabledegreeofaccuracy.This
∆h = heat of combustion of CO, kJ/kg,
CO
critical temperature is the ignition temperature. It is higher for
˙
D" = depletion rate of oxygen per unit surface area,
O
unpiloted ignition than for piloted ignition. For each of the
kg/m ·s,
ignition modes, however, ignition temperature is a character-
k = mass oxygen-to-fuel stoichiometric ratio, kg/kg,
O
istic of the material and does not vary with heat flux. SI units
k = maximum possible yield of CO , kg/kg,
CO 2
are degrees Celsius or Kelvin.
k = maximum possible yield of CO, kg/kg,
CO
6.10.1.4 Some investigators have actually measured surface
G" = generation rate of CO , kg/m ·s, and
CO 2
G" = generation rate of CO, kg/m ·s. temperature at ignition and showed that it is a reasonable
CO
criterion for engineering analyses (16, 17).
6.9.3 Apparatus to Be Used:
6.10.2 Procedures to Obtain Ignition Temperature:
6.9.3.1 The heat release rate can be estimated by measuring
6.10.2.1 Ignition temperatures may be obtained in two
the sensible enthalpy of the fire gas outflow. The Ohio State
ways.The first is by actually measuring surface temperature in
University apparatus (Test Method E906) applies this
ignition tests. Various investigators have attached very fine
principle, but it has proven difficult and generally inaccurate.
thermocouples (5 mil or less) to the surface of the specimen
Most heat release rate measurement devices currently use the
(17, 18). This method is very tedious a
...

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: E1591 − 13 E1591 − 20 An American National Standard
Standard Guide for
Obtaining Data for Fire Growth Models
This standard is issued under the fixed designation E1591; 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 guide describes data required as input for mathematical fire growth models.
1.2 Guidelines are presented on how the data can be obtained.
1.3 The emphasis in this guide is on ignition, pyrolysis and flame spread models for solid materials.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 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.
1.6 This fire standard cannot be used to provide quantitative measures.
1.7 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:
C177 Test Method for Steady-State Heat Flux Measurements and Thermal Transmission Properties by Means of the
Guarded-Hot-Plate Apparatus
C518 Test Method for Steady-State Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus
C835 Test Method for Total Hemispherical Emittance of Surfaces up to 1400°C
C1371 Test Method for Determination of Emittance of Materials Near Room Temperature Using Portable Emissometers
D2395 Test Methods for Density and Specific Gravity (Relative Density) of Wood and Wood-Based Materials
D3417 Test Method for Enthalpies of Fusion and Crystallization of Polymers by Differential Scanning Calorimetry (DSC)
(Withdrawn 2004)
D5865 Test Method for Gross Calorific Value of Coal and Coke
D7309 Test Method for Determining Flammability Characteristics of Plastics and Other Solid Materials Using Microscale
Combustion Calorimetry
E176 Terminology of Fire Standards
E408 Test Methods for Total Normal Emittance of Surfaces Using Inspection-Meter Techniques
E472 Practice for Reporting Thermoanalytical Data (Withdrawn 1995)
E537 Test Method for Thermal Stability of Chemicals by Differential Scanning Calorimetry
E793 Test Method for Enthalpies of Fusion and Crystallization by Differential Scanning Calorimetry
E906 Test Method for Heat and Visible Smoke Release Rates for Materials and Products Using a Thermopile Method
E967 Test Method for Temperature Calibration of Differential Scanning Calorimeters and Differential Thermal Analyzers
E968 Practice for Heat Flow Calibration of Differential Scanning Calorimeters
E1321 Test Method for Determining Material Ignition and Flame Spread Properties
E1354 Test Method for Heat and Visible Smoke Release Rates for Materials and Products Using an Oxygen Consumption
Calorimeter
This guide is under the jurisdiction of ASTM Committee E05 on Fire Standards and is the direct responsibility of Subcommittee E05.33 on Fire Safety Engineering.
Current edition approved April 1, 2013April 1, 2020. Published May 2013May 2020. Originally approved in 1994. Last previous edition approved in 20072013 as
E1591–07.–13. DOI: 10.1520/E1591-13.10.1520/E1591-20.
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.
The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1591 − 20
E1537 Test Method for Fire Testing of Upholstered Furniture
E1623 Test Method for Determination of Fire and Thermal Parameters of Materials, Products, and Systems Using an
Intermediate Scale Calorimeter (ICAL)
E2058 Test Methods for Measurement of Material Flammability Using a Fire Propagation Apparatus (FPA)
E2257 Test Method for Room Fire Test of Wall and Ceiling Materials and Assemblies
3. Terminology
3.1 Definitions—For definitions of terms appearing in this guide, refer to Terminology E176.
4. Significance and Use
4.1 This guide is intended primarily for users and developers of mathematical fire growth models. It is also useful for people
conducting fire tests, making them aware of some important applications and uses for small-scale fire test results. The guide thus
contributes to increased accuracy in fire growth model calculations, which depend greatly on the quality of the input data.
4.2 The emphasis of this guide is on ignition, pyrolysis and flame spread models for solid materials.
5. Summary of Guide
5.1 This guide provides a compilation of material properties and other data that are needed as input for mathematical fire growth
models. For every input parameter, the guide includes a detailed description and information on how it can be obtained.
5.2 The following input parameters are discussed: 6.1, combustion efficiency; 6.2, density; 6.3, emissivity; 6.4, flame extinction
coefficient; 6.5, flame spread parameter; 6.6, heat of combustion; 6.7, heat of gasification; 6.8, heat of pyrolysis; 6.9, heat release
rate; 6.10, ignition temperature; 6.11, mass loss rate; 6.12, production rate of species; 6.13, pyrolysis temperature; 6.14, specific
heat; 6.15, thermal conductivity; and 6.16, thermal inertia.
5.3 Some guidance is also provided on where to find values for the various input parameters.
6. Data for Fire Growth Models
6.1 Combustion Effıciency:
6.1.1 Introduction—The effective heat of combustion in fires is smaller than the net heat of combustion because of the
incomplete combustion of fuel vapors. The combustion efficiency, χ, accounts for incomplete combustion.
6.1.2 Procedures to Obtain Combustion Effıciency—The ratio between the effective heat of combustion and net heat of
combustion is the combustion efficiency. Thus,
Δh
c,eff
χ5 (1)
Δh
net
where:
Δh = effective heat of combustion, kJ/kg, and
c,eff
Δh = net heat of combustion, kJ/kg.
c,net
The combustion efficiency for most hydrocarbons ranges from 0.4 to 0.9.
6.1.3 Apparatus to Be Used:
6.1.3.1 Test Method D5865 for Δh (with adjustment for water vapor; see 6.6); and
c,net
6.1.3.2 Cone Calorimeter (Test Method E1354), ICAL Apparatus (Test Method E1623), or the Fire Propagation Apparatus
(Test Method E2058) for Δh (see 6.6).
c,eff
6.2 Density:
6.2.1 Introduction:
6.2.1.1 The density of a material is the mass of material per unit volume. In fire models, density is usually expressed as kg/m .
6.2.1.2 There are two reasons for density to change as a material is heated: volatile (flammable or nonflammable, or both) may
be lost and dimensional changes (expansion or contraction) may occur. Although corrections for temperature dependence can be
made (1), many models use constant (room) temperature values.
6.2.2 Procedures to Obtain Density:
6.2.2.1 The density of a material is determined by measuring the mass and physical dimensions (volume) of a sample of the
material. There are detailed ASTM guidelines for certain types of building materials, for example, Test Methods D2395 for wood
and wood-base materials.
6.2.2.2 When the temperature dependence of density is sought, changes in mass with temperature can be determined using
thermogravimetric analysis and changes in dimensions with temperature using dilatometric analysis (1, 2).
6.2.3 Apparatus to Be Used:
The boldface numbers in parentheses refer to a list of references at the end of this standard.
E1591 − 20
6.2.3.1 Mass Balance (or equivalent).
6.2.3.2 Caliper, Ruler (or equivalent).
6.2.3.3 Dilatometric Apparatus.Apparatus .
6.2.3.4 Thermogravimetric Analyzer.Analyzer .
6.3 Emissivity:
6.3.1 Introduction—The emissivity of a material is the ratio of the power per unit area radiated from its surface to that radiated
from a black body at the same temperature. A material’s emissivity represents its thermal radiative behavior integrated over all
wavelengths. Emissivity is a dimensionless quantity with an upper limit of unity for a black body.
6.3.2 Procedures to Obtain Emissivity— Several standard test methods have been developed to measure the emissivity of
materials. A specimen of the material is usually placed in an evacuated chamber and heated (often with an electric current) to the
temperature of interest. The power dissipated by the material is determined and equated to the radiative heat transfer to the
surroundings. The emissivity of the material is computed using this power and the Stefan-Boltzman equation.
6.3.3 Apparatus to Be Used:
6.3.3.1 Vacuum Emittance Test Apparatus (Test Method C835).
6.3.3.2 Portable Emissometer (Test Methods C1371).
6.3.3.3 Inspection Meter (Test Methods E408).
6.4 Flame Extinction Coeffıcient:
6.4.1 Introduction—The flame extinction coefficient interrelates average radiation parameters such as emissivity, flame intensity,
and temperature over the entire spectrum of wavelengths. It is used in the following equation to calculate the emissive power of
a flame:
˙ A 2kl
E 5 AσT 12 e (2)
~ !
f
where:
E = emissive power of the flame, W,
A = enveloping area of the flame, m ,
−8 2 4
σ = Boltzman constant, 5.67·10 W/m ·K ,
T = flame temperature, K,
f
−1
k = flame extinction coefficient, m , and
l = path length, m.
k is also called the absorption coefficient, absorption-emission coefficient, or effective emission coefficient.
6.4.2 Procedures to Obtain Flame Extinction Coeffıcient—The coefficient k can be estimated from measurement of the
−kl
emissivity ε and path length l, assuming emissivity can be expressed as ε = 1 − e .
6.4.3 Apparatus to Be Used—There is no apparatus for measuring the flame extinction coefficient. The extinction coefficient can
be determined by measuring all flame parameters in the equation for Ė except k. Fire models include many of such empirical
equations, but the documentation usually does not specify what the parameters mean and how they are to be determined. It must
be stressed that the equation for Ė is highly empirical. This makes it essential that the flame area, flame temperature, and extinction
coefficient be determined in a self-consistent manner.
6.5 Flame Spread Parameter:
6.5.1 Introduction:
6.5.1.1 The opposed-flow (against the direction of the surrounding flow or against gravity) flame spread rate over a surface can
be predicted via the equation originally developed by deRis (3):
φ
V 5 (3)
p 2
kρc T 2 T
~ !
ig s
where:
V = flame travel rate, m/s,
p
2 3
φ = flame spread parameter, W /m ,
k = thermal conductivity, W/m·K,
ρ = density, kg/m ,
c = heat capacity, J/kg·K,
T = surface temperature at ignition, K, and
ig
T = surface temperature just prior to arrival of the flame front, K.
s
6.5.1.2 The flame spread parameter, φ, for specific orientations and in standard air environments is a characteristic for the heat
transfer from the flame to the fuel ahead of the flame front in the vicinity of the flame foot. It is a material property expressed in
2 3
W /m .
6.5.2 Procedures to Obtain the Flame Spread Parameter—The flame spread parameter can be obtained from a correlation of
opposed-flow flame spread data, that is, flame spread rate over a range of irradiance levels (or surface temperatures). The test
E1591 − 20
method described in Test Method E1321 was developed specifically to measure the flame spread parameter. It must be stressed that
the equation for V is highly empirical. This makes it essential that V , kρ c, and T be determined in a self-consistent manner.
p p ig
Further details on consistent methods to determine T and kρc can be found in 6.10 and 6.16, respectively.
ig
6.5.3 Apparatus to Be Used:
6.5.3.1 LIFT Apparatus (Test Method E1321).
6.6 Heat of Combustion:
6.6.1 Introduction—All combustion reactions generate energy, which may be expressed as heat. The heat of combustion is
defined as the amount of heat generated when a unit quantity of fuel is oxidized completely. SI units for heat of combustion, Δh ,
c
is kJ/kg.
6.6.2 Procedures to Obtain Heat of Combustion:
6.6.2.1 Heats of combustion are measured by combustion bomb calorimetry. A known mass of fuel is burned completely in an
adiabatic apparatus containing pure oxygen. This method yields the gross heat of combustion. The net heat of combustion can be
determined by subtracting the latent heat of evaporation (2.26 kJ/kg of water) from the gross heat of combustion.
6.6.2.2 An effective heat of combustion can be obtained from other tests that use oxygen calorimetry. For example, the cone
calorimeter (Test Method E1354) measures the mass loss rate and heat release rate. Incomplete combustion may occur in this
environment. The effective heat of combustion, Δh , is the ratio between heat release rate and mass loss rate.
c,eff
q˙
Δh 5 (4)
c,eff
m˙
where:
q˙ = heat release rate, kW, and
m˙ = mass loss rate of the sample, kg/s.
6.6.3 Apparatus to Be Used:
6.6.3.1 Oxygen Bomb Calorimetry (Test Method D5865).
6.6.3.2 Cone Calorimeter (Test Method E1354).
6.6.3.3 ICAL Apparatus (Test Method E1623).
6.6.3.4 Furniture calorimeter.Calorimeter (Test Method E1537).
6.6.3.5 Microscale Combustion Calorimeter (Test Method D7309).
6.7 Heat of Gasification:
6.7.1 Introduction—The heat of gasification of a material is equal to the net amount of heat that must be supplied through its
exposed surface to convert a mass unit to gaseous volatiles.
"
q˙
net
Δh 5 (5)
g
m˙ "
where:
q˙" = net heat flux into the material, kW/m , and
net
m˙" = mass loss rate of the material, kg/m ·s.
Δh = heat of gasification, kJ/kg.
g
6.7.2 Procedures to Obtain Heat of Gasification:
6.7.2.1 For a flaming sample, the net heat flux conducted into the material is equal to the sum of radiation and convection from
the flame and the external heat flux (from the radiant heater in a small-scale test), minus the (radiant) heat losses from the surface.
The flame flux and heat losses depend on the surface temperature, which is very difficult to measure. The cone calorimeter (Test
Method E1354) has been used, in conjunction with surface temperature measurements, to determine Δh for wood products and
g
PMMA.
6.7.2.2 For some materials, the surface temperature is reasonably constant and independent of exposure conditions. A plot of
(mean or peak) mass loss rates as a function of external irradiance yields a fairly linear relationship for such materials. Values of
Δ h can then be estimated from the inverse of the slope of the regression line through the data points. Tewarson and Petrella have
g
used this technique to obtain Δh values for a wide range of plastics (4, 5).
g
6.7.2.3 Unfortunately, surface temperatures are not constant for many materials, in particular charring materials and materials
with a high smoke yield. The method by Tewarson and Petrella can still be used, but it yields results that have little physical
meaning. Various investigators have used the version of the equation for Δh and have obtained a time-dependent heat of
g
gasification curve instead of a single value (6-78)
6.7.3 Apparatus to Be Used:
6.7.3.1 Cone Calorimeter (Test Method E1354).
6.7.3.2 ICAL Apparatus (Test Method E1623).
6.7.3.3 Fire Propagation Apparatus (Test Method E2058).
6.8 Heat of Pyrolysis (Heat of Reaction):
E1591 − 20
6.8.1 Introduction:
6.8.1.1 Chemical reactions generally involve the generation or absorption of energy. The heat of pyrolysis is the energy emitted
or lost during the pyrolysis or thermal degradation of material. It is also defined as the difference between the enthalpy of the virgin
material and the enthalpy of the pyrolysis products. In the calculation of the heat of reaction, the products are assumed to be at
the pyrolysis temperature, and the virgin material is assumed to be at the ambient temperature. SI units of the heat of pyrolysis
are kJ/kg. It is sometimes expressed in kJ/m in models.
6.8.1.2 Bench scale tests generally measure the heat of pyrolysis of a small sample exposed to well-prescribed thermal
conditions. Heat of pyrolysis or the corresponding change in enthalpy is usually an input parameter in the energy balance equation
for a solid material undergoing thermal degradation.
6.8.1.3 The heat of pyrolysis is generally found in models that calculate the temperature profile within a solid material as it is
being heated. The internal energy generation term can be represented in several different ways depending on model. One common
way is to multiply the heat of pyrolysis Q (in kJ/kg) by the local rate of decomposition (in kg/m ·s) to obtain the energy generation
term. An alternative is simply to use an energy generation term dE/dt (in kW/m ). An alternative for Q is to input the specific heat
capacities and enthalpies of formation and have the computer program calculate the enthalpies and corresponding heat of pyrolysis
Q. Some models will not have a heat of pyrolysis term since the net energy change is assumed to be zero. The energy generation
term may also include sensible energy as well as energy change due to pyrolysis.
6.8.2 Procedures to Obtain Heat of Pyrolysis:
6.8.2.1 The most common experimental procedure to measure the heat of pyrolysis is differential scanning calorimetry (DSC).
A small quantity (a few mg) of sample is placed in the apparatus. Thermal degradation is obtained using a specified
time-temperature exposure. Heat is added to the sample and an inert reference compound so the two materials are maintained at
identical temperatures. The added heat is recorded and is assumed to equal the energy lost or gained as a result of the endothermic
or exothermic reaction. The sample environment is purged with nitrogen or another inert gas when oxidation reactions are not to
be considered. DSC results are affected by such factors as particle size and heating rate. Because of these factors, it can be argued
that the DSC results for such small samples are not representative of the behavior of the material in practice. DSC procedures are
also used to measure the enthalpy gain or loss associated with physical processes such as vaporization and desorption, as well as
the specific heat capacity of a material.
6.8.2.2 The heat of pyrolysis (Δ h ) is generally considered negative for exothermic reactions and positive for endothermic
p
reactions. DSC results are usually presented as a curve, with the energy input on the ordinate with upward deflection reflecting an
exothermic reaction and time or temperature on the abscissa increasing from left to right. Standard practices for reporting
thermoanalytical data are given in Practice E472.
6.8.2.3 An alternative thermal analysis is differential thermal analysis (DTA). The temperature difference between the sample
and the reference material is measured in DTA as a function of temperature. Quantitative results for the heat of pyrolysis can be
calculated from DTA results. Thermogravimetry (TGA) can be used to measure the mass loss as a function of temperature.
6.8.2.4 Estimates for heat of pyrolysis have also been calculated from other measurements. One alternative to measuring the
heat of reaction is to add the enthalpies of the pyrolysis products and subtract them from the enthalpy of the virgin material.
Another procedure that has been used is to develop a transient heat balance model that has the heat of pyrolysis as the unknown.
The energy balance equation is solved for the heat of pyrolysis based on experimentally obtained temperature profile data.
6.8.2.5 The methods mentioned above are not suitable for layered composite materials.
6.8.3 Apparatus to Be Used:
6.8.3.1 Several commercial instruments are available and are generally designed to perform other types of thermal analysis as
well as DSC. The basic components of the DSC are the sample containers, heating unit, programmable temperature controller, inert
reference material, and measuring and recording devices.
6.8.3.2 DSC procedures and apparatuses are discussed in Test Methods D3417, E537, and E793. Power-compensation DSC and
heat-flux DSC are two types of apparatuses. Calibration of DSC equipment is discussed in Practices E967 and E968.
6.9 Heat Release Rate:
6.9.1 Introduction—A realistic calculation of the effects of fire requires knowledge of the burning rate. The burning rate can be
expressed as the mass generation rate of fuel volatile or as a rate of heat release q˙. The units of heat release rate are W or kW.
6.9.2 Procedures to Obtain Heat Release Rate:
6.9.2.1 The rate of heat release cannot be predicted from basic measurements of material properties; it is a function of the
thermal environment, fuel volatilization, and efficiency of volatile combustion. The heat release rate and mass loss rate are related
by the following equation:
q˙ 5 m˙ χΔh (6)
c,net
where:
Δh = net heat of combustion of the volatile, kJ/kg,
c,net
χ = combustion efficiency, and
m˙ = mass loss rate of fuel, kg/s.
E1591 − 20
6.9.2.2 The heat release rate can also be estimated by assuming that heat is generated by a reaction in which only H O, CO ,
2 2
and CO are produced, and O is depleted (89, chapter 3). The heat release rate, q˙, can be calculated from the following equations
(910):
Δh
c,net
˙ "
q˙ "5 D (7)
O
k
O
and
Δh Δh 2 Δ h
c,net c,net CO
˙ " ˙ "
q˙ "5 G 1 G (8)
CO CO
k k
CO CO
where:
q˙" = heat release rate per unit area, kW/m ,
Δh = net heat of complete combustion of the material, kJ/kg,
c,net
Δh = heat of combustion of CO, kJ/kg,
CO
D˙" = depletion rate of oxygen per unit surface area, kg/m ·s,
O
k = mass oxygen-to-fuel stoichiometric ratio, kg/kg,
O
k = maximum possible yield of CO , kg/kg,
CO 2
k = maximum possible yield of CO, kg/kg,
CO
G" = generation rate of CO , kg/m ·s, and
CO 2
G" = generation rate of CO, kg/m ·s.
CO
6.9.3 Apparatus to Be Used:
6.9.3.1 The heat release rate can be estimated by measuring the sensible enthalpy of the fire gas outflow. The Ohio State
University apparatus (Test Method E906) applies this principle, but it has proven difficult and generally inaccurate. Most heat
release rate measurement devices currently use the oxygen calorimetry principle (1011) as implemented in the cone calorimeter
(Test Method E1354). One can use the following for small-scale measurements:
(1) Ohio State University Calorimeter (Test Method E906), preferably modified for oxygen consumption (11-12-1314).
(2) Cone Calorimeter (Test Method E1354).
(3) Fire Propagation Apparatus (Test Method E2058).
6.9.3.2 Large-scale measurements can be obtained with the following:
(1) ICAL Apparatus (Test Method E1623).
(2) Furniture Calorimeter (Test Method E1537).
(3) Factory Mutual Fire Products Collection Calorimeter(1415).
(4) Room/Corner Test(Test Method E2257).
6.9.3.3 These large-scale tests are usually overventilated. Ventilation limits and thermal feedback from the upper smoke layer
and walls may have to be accounted for when applying the data to room fire models.
6.10 Ignition Temperature:
6.10.1 Introduction:
6.10.1.1 Ignition of a solid fuel is defined as the initiation of flaming combustion in the gas phase. When a solid material is
exposed to external heat, at some point it will begin to pyrolyze. The fuel vapors mix with air in the boundary layer. Shortly
thereafter, the pyrolysis rate may be sufficient for the lower flammability limit to be reached. This mixture will ignite under certain
conditions.
6.10.1.2 A distinction should be made between two types of ignition:
(1) Piloted Ignition—Flaming combustion of the gas mixture initiates at a small pilot present in the gas phase. This pilot may
be a gas flame, an electric spark, or a glowing wire. Temperature is high enough locally around the pilot for the combustion
reactions to start, provided the mixture is flammable.
(2) Unpiloted Ignition—If there is no pilot, the surface of the solid must reach a sufficiently high temperature to trigger the
combustion reactions.
6.10.1.3 The prediction of when a solid fuel ignites if exposed to a certain heat flux is a very difficult problem. It includes
consideration of heat and mass transfer, in both the solid and gas phases, and fluid flow and mixing in the gas phase. Many
investigators have assumed a critical surface temperature criterion for ignition in order to simplify the problem while maintain an
acceptable degree of accuracy. This critical temperature is the ignition temperature. It is higher for unpiloted ignition than for
piloted ignition. For each of the ignition modes, however, ignition temperature is a characteristic of the material and does not vary
with heat flux. SI units are degrees Celsius or Kelvin.
6.10.1.4 Some investigators have actually measured surface temperature at ignition and showed that it is a reasonable criterion
for engineering analyses (1516, 1617).
6.10.2 Procedures to Obtain Ignition Temperature:
6.10.2.1 Ignition temperatures may be obtained in two ways. The first is by actually measuring surface temperature in ignition
tests. Various investigators have attached very fine thermocouples (5 mil or less) to the surface of the specimen (1617, 1718). This
E1591 − 20
method is very tedious as it is difficult to handle fine thermocouples and to ensure good contact with the surface. A more practical
technique for monitoring surface temperature is via a narrow angle infrared pyrometer aimed at a small spot on the surface.
However, a pyrometer measures thermal radiation rather than surface temperature. This radiation is partly emission, but also
reflection, from the surface. Since surface characteristics (emissivity, absorptivity, and reflectivity) change during exposure and are
usually known only roughly, the calculation of surface temperature from pyrometer readings is not trivial.
6.10.2.2 The other way of obtaining surface temperature is through the application of some ignition theory to a set of ignition
test results. The results are a series of times to (piloted or unpiloted) ignition at various heat flux levels. Such data can be obtained
in any apparatus that is capable of exposing specimens over a range of heat flux levels such as Test Methods E906, E1321, or
E1354.
6.10.2.3 A comprehensive theory for interpreting piloted ignition data obtained in the LIFT apparatus (Test Method E1321) was
developed by Quintiere, et al. (1718). The critical heat flux, that is, the irradiance level below which piloted ignition no longer
occurs, is found experimentally. Ignition temperature then follows from a heat balance equation at the spec
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