ASTM C1057-22

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: C1057 − 17 C1057 − 22
Standard Practice for
Determination of Skin Contact Temperature from Heated
Surfaces Using a Mathematical Model and
Thermesthesiometer
This standard is issued under the fixed designation C1057; 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 practice covers a procedure for evaluating the skin contact temperature for heated surfaces. Two complimentary
procedures are presented. The first is a purely mathematical approximation that can be is used during design or for worst case
evaluation. The second method describes the thermesthesiometer, an instrument that analogues the human sensory mechanism and
can beis only used only on operating systems.
NOTE 1—Both procedures listed herein are intended for use with Guide C1055. When used in conjunction with that guide, these procedures can determine
the burn hazard potential for a heated surface.
1.2 A bibliography of human burn evaluation studies and surface hazard measurement is provided in the References at the end
of Guide C1055. Thermesthesiometer and mathematical modeling references are provided in the References at the end of this
practice (1-5).
1.3 This practice addresses the skin contact temperature determination for passive heated surfaces only. The analysis procedures
contained herein are not applicable to chemical, electrical, or other similar hazards that provide a heat generation source at the
location of contact.
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 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 practice is under the jurisdiction of ASTM Committee C16 on Thermal Insulation and is the direct responsibility of Subcommittee C16.30 on Thermal Measurement.
Current edition approved May 1, 2017May 1, 2022. Published June 2017May 2022. Originally approved in 1986. Last previous edition approved in 20122017 as
C1057 – 12.C1057 – 17. DOI: 10.1520/C1057-17.10.1520/C1057-22.
The boldface numbers in parentheses refer to the list of references at the end of this practice.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. 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
C1057 − 22
C168 Terminology Relating to Thermal Insulation
C680 Practice for Estimate of the Heat Gain or Loss and the Surface Temperatures of Insulated Flat, Cylindrical, and Spherical
Systems by Use of Computer Programs
C1055 Guide for Heated System Surface Conditions that Produce Contact Burn Injuries
3. Terminology
3.1 Definitions—Terminology C168 shall be considered as applicable to the terms used in this standard.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 acceptable contact time—the limit of time of contact for the heated surface and the exposed skin. Practice has suggested
limits of 5 s for industrial processes and up to 60 s for consumer items.
3.2.2 burns:
3.2.2.1 first degree burn—the reaction to an exposure where the intensity and duration is insufficient to cause complete necrosis
of the epidermal layer. The normal response to this level of exposure is dilation of the superficial blood vessels (reddening of the
skin).
3.2.2.2 second degree burn—the reaction to an exposure where the intensity and duration is sufficient to cause complete necrosis
of the epidermis but no significant damage to the dermis. The normal response to this exposure is blistering of the epidermis.
3.2.2.3 third degree burns—the reaction to an exposure where significant dermal necrosis occurs. Significant dermal necrosis has
been defined in the literature as a 75 % destruction of the dermis thickness. The normal response to this exposure is open sores
that leave permanent scar tissue upon healing.
3.2.3 skin:
3.2.3.1 epidermis—the outermost layer of skin cells. This layer contains no vascular or nerve cells and acts to protect the outer
skin layers. The thickness of this layer averages 0.08 mm.
3.2.3.2 dermis—the second layer of skin tissue. This layer contains blood vessels and nerve endings. The thickness of this layer
is about 2 mm.
3.2.3.3 necrosis—localized death of living cells. This is a clinical term that defines when damage to the skin layer has occurred.
3.2.4 skin contact temperature—the temperature of the skin at a depth of 0.08 mm reached after contact with a heated surface for
a specified time.
3.2.5 thermal inertia—a measure of the responsiveness of a material to variations in temperature. This property is also known as
thermal effusivity.
3.2.6 thermesthesiometer—an electromechanical device developed by L. A. Marzetta at National Institute of Standards and
Technology to analogue the touch response of the human skin when it contacts a heated surface. This measurement concept holds
U.S. Patent No. 3,878,728 dated April 22, 1975, and was assigned to the USA as represented by the Department of Health and
Welfare. No known restriction exists to limit the development of units based upon this principle.
4. Summary of Practice
4.1 This practice provides two procedures for evaluation of the skin contact temperature from heated surfaces. Either of the two
methods, a mathematical model and a physical measurement, can be is used depending upon the availability of the system (that
is, is it built and operating or is it in the design state) and the operating conditions. The first step in using this practice is to
determine which procedure is to be used. Unless the system of interest is operating at design “worst case” conditions, such as high
system temperatures and high ambient temperature, the calculational procedure is recommended. On the other hand, if the question
is safety at the present conditions, the thermesthesiometer provides a quick measurement with no auxiliary calculations. Paragraphs
4.2 and 4.3 outline the two alternative procedures available.
C1057 − 22
4.2 Calculational Procedure, Method A—First the surface temperature of the insulated system is determined by either a direct
measurement, using either thermocouples, thermistors, or infrared noncontact techniques, or by modeling of the system using
Practice C680. Once the surface temperature is known, the designer uses the equation set to estimate the maximum epidermal
contact temperature for the acceptable contact time. This temperature is a function of surface temperature, time of contact, and
composition of both the surface material and substrate. The designer then refers to Guide C1055 to determine the burn hazard
potential of the surface.
4.3 Thermesthesiometer, Method B—The operator places the calibrated sensor probe face firmly against the heated surface for the
acceptable contact time. The device directly reads the contact temperature from the probe. The maximum temperature is used in
conjunction with the Guide C1055 to determine the burn hazard potential of the surface.
5. Significance and Use
5.1 The procedures in this practice support the determination of the burn hazard potential for a heated surface. These procedures
provide an estimate of the maximum skin contact temperature and must be used in conjunction with Guide C1055 to evaluate the
surface hazard potential.
5.2 The two procedures outlined herein are both based upon the same heat transfer principles. Method A uses a mathematical
model to predict the contact temperature, while Method B uses a plastic rubber probe having similar heat transfer characteristics
to the human finger to “measure” the contact temperature on real systems.
5.3 These procedures serve as an estimate for the skin contact temperatures which might occur for the “average” individual.
Unusual conditions of exposure, incorrect design assumptions, subject health conditions, or unforeseen operating conditions may
will potentially negate the validity of the estimations.
5.4 These procedures are limited to direct contact exposure only. Conditions of personal exposure to periods of high ambient
temperatures, direct flame exposure, or high radiant fluxes may will potentially cause human injury in periods other than
determined herein. Evaluation of exposures other than direct contact are beyond the scope of this practice.
5.5 Cold Surface Exposure—No consensus criteria exists for the destruction of skin cells by freezing. If, at some future time, such
criteria are developed, extrapolation of the techniques presented here will serve as a basis for cold surface exposure evaluation.
6. Method A—Use of the Mathematical Model
6.1 This modeling approach is for use when the system is being designed or, if for some reason, it cannot be operated at design
conditions. The model approximates the transient heat flow phenomena of the skin contacting a hot surface using the equation set
described by Dussan and Weiner (1) and Wu (5). The user is required to make certain definitions of system geometry and materials,
the system operating conditions, and the allowable time of exposure. After definition of the input values, the equation set yields
an estimate of the skin contact temperature needed for the hazard evaluation. The user must realize that as with all mathematical
approximations, the estimate is only as good as the input data. Where some input parameter is known only within some range of
values, a sensitivity analysis about that range is recommended.
6.2 The first step in estimating the effective skin contact temperature is to identify and record the following information describing
the system as input for the model:
6.2.1 System Description—Geometry, location, accessibility.
6.2.2 Present/Design Operating Conditions—Duty cycle, operating temperatures of equipment.
6.2.3 System/Surface Data (as appropriate)—Substrate (insulation) type and thickness, jacket type and thickness, surface
properties, such as emissivity and condition, shiny, painted, dirty, corroded.
6.2.4 Ambient Conditions, including dry bulb temperature and local wind velocity.
NOTE 2—The design temperatures should be at the worst case (generally high operating and high ambient) conditions. Care should be used in the selection
C1057 − 22
of design conditions since the hazard design conditions are different from the heat loss design conditions.
6.3 Using Practice C680 or a compatible program and the information gathered in 6.2, calculate the maximum operating surface
temperature. This temperature is an input to the model for the contact temperature.
6.3.1 Where the system is operating at design conditions, perform a direct measurement can be used to determine the surface
temperature. Thermocouples, resistance thermometers, or other means can be used; are options; however, proper application
techniques are required for accurate results. Caution must be observed since the surface temperature may be high high surface
temperatures are present and the surface could constitute is a potential burn hazard.
6.4 Calculate the expected skin contact temperature versus time history using the procedure below based upon the hot surface
temperature, time of contact, and system properties. The development of the equations below is taken from Dussan and Weiner
(1). A more detailed derivation of the equation set used is included in the papers by Dussan and Weiner (1) and Wu (5). See Fig.
1.
6.4.1 Calculate the initial parameter constants, using Eq 4-11.
6.4.2 The contact temperature for the skin can now be is determined using Eq 1, Eq 2, and Eq 3 together for the system in question.
Note that the solution to this equation is a sum of an infinite series. The solution, however, converges quickly (five or six terms)
and can be is easily handled manually or by a small computer.
` `
N N
T 5 T 1A I erfc ~θ !1B I erfc ~θ' ! (1)
c 0 ( N ( N
N50 N50
and:
= =
X / α 12·N·l/ α
1 1 2
θ 5 (2)
N
=
2 t
= =
X / α 12·~N11!·l/ α
1 1 2
θ' 5 (3)
N
2=t
P 2 P · P 2 P
~ ! ~ !
2 3 2 1
I 5 (4)
~P 1P !·~P 1P !
2 3 2 1
~T 2 T !·P
i 0 2
A 5 (5)
P 1P
2 1
T 2 T · P 2 P ·P
~ ! ~ !
i 0 3 2 2
B 5 (6)
~P 1P !·~P 1P !
2 3 2 1
1/2
P 5 ρ ·C ·K (7)
~ !
1 1 1 1
1/2
P 5 ρ ·C ·K (8)
~ !
2 2 2 2
FIG. 1 Schematic of Heat Transfer Model
C1057 − 22
1/2
P 5 ρ ·C ·K (9)
~ !
3 3 3 3
α 5 K /ρ ·C (10)
1 1 1 1
α 5 K /ρ ·C (11)
2 2 2 2
where:
T = initial tissue temperature, °C,
N = integral constant, 1 > ∞,
−5
X = depth of tissue of interest, normally 8.0 × 10 m,
α = thermal diffusivity of layer i, m /s,
i
l = la
...