ASTM F3628-24

Standard Test Method for Measuring the Cooling Energy Provided by Wicking Liquid Moisture and Evaporating It from Clothing Materials Using a Sweating Hot Plate

SIGNIFICANCE AND USE
4.1 A clothing material’s ability to assist in the evaporation of liquid sweat by managing liquid moisture is of considerable importance when trying to maximize cooling and comfort benefits to the wearer while active. Understanding how much energy is released back to the skin is critical in determining their suitability for use in fabricating protective clothing systems or athletic wear.  
4.1.1 The cooling energy released back to the wearer can be significantly affected by environmental conditions. Extreme care must be taken when using standard results measured under standard testing conditions to determine a material’s suitability for use in conditions outside the testing conditions.  
4.2 This test method accounts for a clothing material’s ability to assist in evaporating liquid water during a sweating phase, as well as its ability to dry after the cessation of sweating.  
4.2.1 A large amount of cooling energy released from clothing materials during active work (sweating) is often seen as a positive, as it would assist in keeping the body cooler.  
4.2.2 A large amount of cooling energy released from clothing materials after active work (no sweating) is often seen as a negative, as it known to cause a chilling effect to the wearer.  
4.2.3 The longer it takes for a clothing material to dry after becoming wet is perceived as a negative, as it increases the potential for chilling the wearer.  
4.3 The thermal interchange between people and their environment is, however, an extremely complicated subject that involves many factors in addition to the steady-state resistance values of fabrics, films, coatings, foams, and leathers, including multi-layer assemblies. Therefore, the cooling provided from liquid evaporation may or may not indicate relative merit of a particular material or system for a given clothing application. While a possible indicator of clothing performance, measurements produced by the testing of fabrics have no proven correlation to the perfo...
SCOPE
1.1 This test method covers the measurement of the cooling energy released back to the wearer’s skin by a clothing material’s ability to move and evaporate controlled dosages of water under controlled ambient conditions using a sweating hot plate.  
1.1.1 This test method establishes procedures for measuring the cooling energy during a simulated “sweating” phase and in a drying phase. Calculations are also provided to determine the drying time and how efficient the clothing material is at assisting in the evaporation of liquid water by comparing it to the maximum amount of energy that can be lost.  
1.2 This test method does not address all properties that affect a clothing material’s ability to lose heat from the body. Consider measuring properties such as air permeability, insulation, and evaporative resistance.  
1.3 The values in SI units shall be regarded as standard. No other units of measurement are included in the standard.  
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: 29-Feb-2024
• ICS: 13.340.10 - Protective clothing
• Technical Committee: F23 - Personal Protective Clothing and Equipment
• Drafting Committee: F23.60 - Human Factors

Relations

• Replaces: ASTM F3628-23 - Standard Test Method for Measuring the Cooling Energy Provided by Wicking Liquid Moisture and Evaporating It from Clothing Materials Using a Sweating Hot Plate
• Effective Date: 01-Mar-2024

Overview

ASTM F3628-24 is the Standard Test Method for Measuring the Cooling Energy Provided by Wicking Liquid Moisture and Evaporating it from Clothing Materials Using a Sweating Hot Plate. Developed by ASTM International, this standard offers a scientifically validated method for quantifying how effectively clothing materials manage and evaporate moisture to provide cooling energy to the wearer, under controlled test conditions. The method is significant for evaluating fabrics intended for personal protective equipment (PPE), athletic wear, and other applications where comfort and thermal management are critical.

Key Topics

• Cooling Energy Measurement: The standard focuses on the energy released back to the wearer’s skin by a clothing material's ability to move and evaporate controlled dosages of water, simulating perspiration using a sweating hot plate.
• Sweating and Drying Phases: Procedures are specified for measuring cooling energy during both active sweating (when the material is wet) and during the drying phase (after sweating has ceased).
• Efficiency and Chilling Potential: The standard guides calculation of drying time, cooling efficiency during sweating, and chilling potential after sweating has stopped. These metrics are vital in understanding both the benefits and comfort limitations of a fabric.
• Testing Conditions: The method stipulates strict environmental controls (temperature, humidity, air velocity) to ensure repeatability and comparability of results. The results under standard conditions provide valuable comparative data but may not fully predict performance in all real-world scenarios.
• Limitations: Although the method assesses evaporative cooling, it does not address all material properties influencing thermal comfort, such as air permeability, insulation, and evaporative resistance. These additional properties should be measured for a comprehensive evaluation.

Applications

• Performance Apparel Development: Fabric and garment manufacturers use this standard to select and design materials with optimal moisture management and cooling characteristics for sportswear and activewear.
• Personal Protective Equipment (PPE): Evaluation of protective clothing systems, where heat stress management is vital for wearer safety and comfort.
• Comparative Fabric Testing: Research laboratories and quality control specialists apply this method to benchmark and compare the cooling performance of different textile materials.
• Innovation and R&D: The standard is widely used in the development of next-generation fabrics with advanced wicking, evaporation, and cooling technologies.
• Thermal Comfort Studies: Useful for studies focusing on the relationship between fabric properties and human thermal comfort in various environments.

Related Standards

• ASTM F1494 - Terminology Relating to Protective Clothing, which provides definitions relevant to the test method.
• ASTM F1868 - Standard Test Method for Thermal Resistance, Evaporative Resistance, and Total Heat Loss of Clothing Materials using a Sweating Hot Plate, which measures related properties and may supplement results from ASTM F3628-24.

Practical Value

Implementing ASTM F3628-24 allows industry professionals to:

• Objectively evaluate clothing material performance in terms of cooling energy, drying time, and chilling effect.
• Optimize product design for wearer comfort, safety, and moisture management across various activity levels and environmental conditions.
• Meet regulatory and market requirements for evidence-based claims about moisture management, cooling, and comfort in textiles.

For accurate results and comprehensive evaluation, users should combine this test method with measures of air permeability, insulation, and evaporative resistance, following all safety and reporting requirements as outlined by ASTM International.

Keywords: cooling energy, moisture management, wicking, evaporative cooling, personal protective equipment, athletic wear, thermal resistance, apparel testing, ASTM F3628-24

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: F3628 − 24
Standard Test Method for
Measuring the Cooling Energy Provided by Wicking Liquid
Moisture and Evaporating It from Clothing Materials Using a
Sweating Hot Plate
This standard is issued under the fixed designation F3628; 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.
INTRODUCTION
Clothing is often made of materials that are designed to enhance the pickup and distribution of
liquids (wicking) to promote the evaporation of sweat. Higher amounts of evaporation should lead to
more cooling of the body during active work and less of a chilling effect after active work has stopped.
This is important to individuals wearing PPE or athletic wear to enhance comfort and prevent
overheating while working. Therefore, it is important to isolate and quantify the amount of cooling
provided by a clothing material’s ability to distribute and evaporate liquid away from a heated surface.
Just as important, it’s also important to isolate and quantify the amount of cooling provided and the
amount of time it takes to remove all the liquid after it is no longer being delivered to the surface.
1. Scope 1.5 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 This test method covers the measurement of the cooling
ization established in the Decision on Principles for the
energy released back to the wearer’s skin by a clothing
Development of International Standards, Guides and Recom-
material’s ability to move and evaporate controlled dosages of
mendations issued by the World Trade Organization Technical
water under controlled ambient conditions using a sweating hot
Barriers to Trade (TBT) Committee.
plate.
1.1.1 This test method establishes procedures for measuring
2. Referenced Documents
the cooling energy during a simulated “sweating” phase and in
a drying phase. Calculations are also provided to determine the 2.1 ASTM Standards:
drying time and how efficient the clothing material is at F1494 Terminology Relating to Protective Clothing
assisting in the evaporation of liquid water by comparing it to F1868 Test Method for Thermal Resistance, Evaporative
the maximum amount of energy that can be lost. Resistance, and Total Heat Loss Measurements of Cloth-
ing Materials Using a Sweating Hot Plate
1.2 This test method does not address all properties that
affect a clothing material’s ability to lose heat from the body.
3. Terminology
Consider measuring properties such as air permeability,
3.1 For definitions of protective clothing-related terms used
insulation, and evaporative resistance.
in this test method, refer to Terminology F1494.
1.3 The values in SI units shall be regarded as standard. No
other units of measurement are included in the standard.
4. Significance and Use
1.4 This standard does not purport to address all of the
4.1 A clothing material’s ability to assist in the evaporation
safety concerns, if any, associated with its use. It is the
of liquid sweat by managing liquid moisture is of considerable
responsibility of the user of this standard to establish appro-
importance when trying to maximize cooling and comfort
priate safety, health, and environmental practices and deter-
benefits to the wearer while active. Understanding how much
mine the applicability of regulatory limitations prior to use.
energy is released back to the skin is critical in determining
This test method is under the jurisdiction of ASTM Committee F23 on Personal
Protective Clothing and Equipment and is the direct responsibility of Subcommittee
F23.60 on Human Factors. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved March 1, 2024. Published March 2024. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 2023. Last previous edition approved in 2023 as F3628 – 23. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/F3628-24. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F3628 − 24
their suitability for use in fabricating protective clothing 5.1.3 Cooling Plate—Underneath the test plate and guard, a
systems or athletic wear. cooling plate must be present. This cooling plate must have
sufficient cooling power to keep it at least 0.5 °C cooler than
4.1.1 The cooling energy released back to the wearer can be
the test plate above.
significantly affected by environmental conditions. Extreme
care must be taken when using standard results measured under
5.2 Water Delivery System—A water delivery system must
standard testing conditions to determine a material’s suitability supply a constant and consistent flow to each of the nine sweat
for use in conditions outside the testing conditions. pores embedded in the test plate. The water delivery system
shall have a delivery rate accuracy of 60.1 mL ⁄h for each pore.
4.2 This test method accounts for a clothing material’s
5.2.1 The tubing connecting the water delivery system and
ability to assist in evaporating liquid water during a sweating
the sweating pores shall be sufficiently long enough to have the
phase, as well as its ability to dry after the cessation of
air within in the chamber heat the water to 35 °C prior to
sweating.
entering the test plate.
4.2.1 A large amount of cooling energy released from
5.3 Temperature Control—Separate, independent tempera-
clothing materials during active work (sweating) is often seen
ture control is required for the three sections of the hot plate
as a positive, as it would assist in keeping the body cooler.
(test plate, guard section, and cooling plate). Temperature
4.2.2 A large amount of cooling energy released from
control of the test plate and guard is achieved by independent
clothing materials after active work (no sweating) is often seen
adjustments to the voltage or current, or both, supplied to the
as a negative, as it known to cause a chilling effect to the
heaters using solid-state power supplies, solid-state relays
wearer.
(proportional time on), adjustable transformers, variable
4.2.3 The longer it takes for a clothing material to dry after impedances, or intermittent heating cycles. The cooling plate
becoming wet is perceived as a negative, as it increases the can provide cooling with liquid heat exchanger. The test plate,
guard, and cooling plate sections shall be controlled to measure
potential for chilling the wearer.
the temperature to within 60.1 °C.
4.3 The thermal interchange between people and their
5.4 Heat Flux Measuring Instrument—Heat lost or gained
environment is, however, an extremely complicated subject
from the surface of the test plate shall be measured to provide
that involves many factors in addition to the steady-state
an accurate average over the period of the test. Overall
resistance values of fabrics, films, coatings, foams, and
accuracy of the measuring device must be within 62 % of the
leathers, including multi-layer assemblies. Therefore, the cool-
reading for the average power for the test period.
ing provided from liquid evaporation may or may not indicate
5.5 Temperature Sensors—Temperature sensors shall be
relative merit of a particular material or system for a given
thermistors, thermocouples, resistance temperature devices
clothing application. While a possible indicator of clothing
(RTDs), or equivalent sensors. The test plate, guard section,
performance, measurements produced by the testing of fabrics
and cooling plate shall each contain one or more temperature
have no proven correlation to the performance of clothing
sensors that are mounted flush with each plate surface and in
systems worn by people. Consider measuring other clothing
such a manner that they measure the surface temperature
material properties such as thermal resistance and evaporative
within 60.1 °C.
resistance when evaluating a clothing material.
4.3.1 The thermal resistance and evaporative resistance of 5.6 Controlled Atmosphere Chamber—The hot plate shall
be housed in an environmental chamber that can be maintained
clothing materials are measured with a standard sweating hot
at selected a temperature of 35 °C. The test chamber wall
plate in an environmental chamber in accordance with Test
temperature shall be 60.5 °C of the air in the chamber. The
Method F1868.
relative humidity shall be maintained as specified in the
individual procedure section.
5. Apparatus
5.7 Measuring Environmental Parameters—The air
5.1 Guarded Sweating Hot Plate—The guarded sweating
temperature, relative humidity, and air velocity shall be mea-
hot plate shall be composed of a test plate surrounded entirely
sured as follows:
by a heated guard section. Below the surface of the plate shall
5.7.1 Relative Humidity Measuring Equipment—Either a
be a cooling plate providing cooling to both the guard and
wet-and-dry bulb psychrometer, a dew point hygrometer, or
testing plate.
other electronic humidity-measuring device shall be used to
5.1.1 Test Plate—The test plate shall be 20.3 cm by 20.3 cm
measure the relative humidity and calculate the dew point
(8 in. by 8 in.) and electrically heated to maintain a constant
temperature inside the chamber. The relative humidity-sensing
temperature in the range of human skin temperature (33 °C to
devices shall have an overall accuracy of at least 64 %.
36 °C). The test plate shall also have nine sweating pores
5.7.2 Air Temperature Sensors—Shielded air temperature
arranged in a three-by-three array for water delivery.
sensors shall be used. Any sensor with an overall accuracy of
5.1.2 Guard Section—The guard section of the guarded
60.1 °C is acceptable. The sensor shall have a time constant
sweating hot plate shall be at least 5.1 cm (2 in.) and surround
not exceeding 1 min. The sensor(s) is suspended with the
the test plate completely. It shall be electrically heated and measuring point exposed to air inside the chamber at a point in
designed to maintain a constant temperature in the range of
the air str
...

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: F3628 − 23 F3628 − 24
Standard Test Method for
Measuring the Cooling Energy Provided by Wicking Liquid
Moisture and Evaporating It from Clothing Materials Using a
Sweating Hot Plate
This standard is issued under the fixed designation F3628; 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.
INTRODUCTION
Clothing is often made of materials that are designed to enhance the pickup and distribution of
liquids (wicking) to promote the evaporation of sweat. Higher amounts of evaporation should lead to
more cooling of the body during active work and less of a chilling effect after active work has stopped.
This is important to individuals wearing PPE or athletic wear to enhance comfort and prevent
overheating while working. Therefore, it is important to isolate and quantify the amount of cooling
provided by a clothing material’s ability to distribute and evaporate liquid away from a heated surface.
Just as important, it’s also important to isolate and quantify the amount of cooling provided and the
amount of time it takes to remove all the liquid after it is no longer being delivered to the surface.
1. Scope
1.1 This test method covers the measurement of the cooling energy released back to the wearer’s skin by a clothing material’s
ability to move and evaporate controlled dosages of water under controlled ambient conditions using a sweating hot plate.
1.1.1 This test method establishes procedures for measuring the cooling energy during a simulated “sweating” phase and in a
drying phase. Calculations are also provided to determine the drying time and how efficient the clothing material is at assisting
in the evaporation of liquid water by comparing it to the maximum amount of energy that can be lost.
1.2 This test method does not address all properties that affect a clothing material’s ability to lose heat from the body. Consider
measuring properties such as air permeability, insulation, and evaporative resistance.
1.3 The values in SI units shall be regarded as standard. No other units of measurement are included in the standard.
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.
This test method is under the jurisdiction of ASTM Committee F23 on Personal Protective Clothing and Equipment and is the direct responsibility of Subcommittee
F23.60 on Human Factors.
Current edition approved Feb. 1, 2023March 1, 2024. Published February 2023March 2024. Originally approved in 2023. Last previous edition approved in 2023 as
F3628 – 23. DOI: 10.1520/F3628-23.10.1520/F3628-24.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F3628 − 24
2. Referenced Documents
2.1 ASTM Standards:
F1494 Terminology Relating to Protective Clothing
F1868 Test Method for Thermal Resistance, Evaporative Resistance, and Total Heat Loss Measurements of Clothing Materials
Using a Sweating Hot Plate
3. Terminology
3.1 For definitions of protective clothing-related terms used in this test method, refer to Terminology F1494.
4. Significance and Use
4.1 A clothing material’s ability to assist in the evaporation of liquid sweat by managing liquid moisture is of considerable
importance when trying to maximize cooling and comfort benefits to the wearer while active. Understanding how much energy
is released back to the skin is critical in determining their suitability for use in fabricating protective clothing systems or athletic
wear.
4.1.1 The cooling energy released back to the wearer can be significantly affected by environmental conditions. Extreme care must
be taken when using standard results measured under standard testing conditions to determine a material’s suitability for use in
conditions outside the testing conditions.
4.2 This test method accounts for a clothing material’s ability to assist in evaporating liquid water during a sweating phase, as well
as its ability to dry after the cessation of sweating.
4.2.1 A large amount of cooling energy released from clothing materials during active work (sweating) is often seen as a positive,
as it would assist in keeping the body cooler.
4.2.2 A large amount of cooling energy released from clothing materials after active work (no sweating) is often seen as a negative,
as it known to cause a chilling effect to the wearer.
4.2.3 The longer it takes for a clothing material to dry after becoming wet is perceived as a negative, as it increases the potential
for chilling the wearer.
4.3 The thermal interchange between people and their environment is, however, an extremely complicated subject that involves
many factors in addition to the steady-state resistance values of fabrics, films, coatings, foams, and leathers, including multi-layer
assemblies. Therefore, the cooling provided from liquid evaporation may or may not indicate relative merit of a particular material
or system for a given clothing application. While a possible indicator of clothing performance, measurements produced by the
testing of fabrics have no proven correlation to the performance of clothing systems worn by people. Consider measuring other
clothing material properties such as thermal resistance and evaporative resistance when evaluating a clothing material.
4.3.1 The thermal resistance and evaporative resistance of clothing materials are measured with a standard sweating hot plate in
an environmental chamber in accordance with Test Method F1868.
5. Apparatus
5.1 Guarded Sweating Hot Plate—The guarded sweating hot plate shall be composed of a test plate surrounded entirely by a
heated guard section. Below the surface of the plate shall be a cooling plate providing cooling to both the guard and testing plate.
5.1.1 Test Plate—The test plate shall be 20.3 cm by 20.3 cm (8 in. by 8 in.) and electrically heated to maintain a constant
temperature in the range of human skin temperature (33 °C to 36 °C). The test plate shall also have nine sweating pores arranged
in a three-by-three array for water delivery.
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.
F3628 − 24
5.1.2 Guard Section—The guard section of the guarded sweating hot plate shall be at least 5.1 cm (2 in.) and surround the test plate
completely. It shall be electrically heated and designed to maintain a constant temperature in the range of human skin temperature
(33 °C to 36 °C).
5.1.3 Cooling Plate—Underneath the test plate and guard, a cooling plate must be present. This cooling plate must have sufficient
cooling power to keep it at least 0.5 °C cooler than the test plate above.
5.2 Water Delivery System—A water delivery system must supply a constant and consistent flow to each of the nine sweat pores
embedded in the test plate. The water delivery system shall have a delivery rate accuracy of 60.1 mL ⁄h for each pore.
5.2.1 The tubing connecting the water delivery system and the sweating pores shall be sufficiently long enough to have the air
within in the chamber heat the water to 35 °C prior to entering the test plate.
5.3 Temperature Control—Separate, independent temperature control is required for the three sections of the hot plate (test plate,
guard section, and cooling plate). Temperature control of the test plate and guard is achieved by independent adjustments to the
voltage or current, or both, supplied to the heaters using solid-state power supplies, solid-state relays (proportional time on),
adjustable transformers, variable impedances, or intermittent heating cycles. The cooling plate can provide cooling with liquid heat
exchanger. The test plate, guard, and cooling plate sections shall be controlled to measure the temperature to within 60.1 °C.
5.4 Heat Flux Measuring Instrument—Heat lost or gained from the surface of the test plate shall be measured to provide an
accurate average over the period of the test. Overall accuracy of the measuring device must be within 62 % of the reading for the
average power for the test period.
5.5 Temperature Sensors—Temperature sensors shall be thermistors, thermocouples, resistance temperature devices (RTDs), or
equivalent sensors. The test plate, guard section, and cooling plate shall each contain one or more temperature sensors that are
mounted flush with each plate surface and in such a manner that they measure the surface temperature within 60.1 °C.
5.6 Controlled Atmosphere Chamber—The hot plate shall be housed in an environmental chamber that can be maintained at
selected a temperature of 35 °C. The test chamber wall temperature shall be 60.5 °C of the air in the chamber. The relative
humidity shall be maintained as specified in the individual procedure section.
5.7 Measuring Environmental Parameters—The air temperature, relative humidity, and air velocity shall be measured as follows:
5.7.1 Relative Humidity Measuring Equipment—Either a wet-and-dry bulb psychrometer, a dew point hygrometer, or other
electronic humidity-measuring device shall be used to measure the relative humidity and calculate the dew point temperature inside
the chamber. The relative humidity-sensing devices shall have an overall accuracy of at least 64 %.
5.7.2 Air Temperature Sensors—Shielded air temperature sensors shall be used. Any sensor with an overall accuracy of 60.1 °C
is acceptable. The sensor shall have a time constant not exceeding 1 min. The sensor(s) is suspend
...