prEN ISO 7933

SLOVENSKI STANDARD
01-januar-2022
Ergonomija toplotnega okolja - Analitično ugotavljanje in razlaga toplotnega
stresa z izračunom predvidene toplotne obremenitve (ISO/DIS 7933:2021)
Ergonomics of the thermal environment - Analytical determination and interpretation of
heat stress using calculation of the predicted heat strain (ISO/DIS 7933:2021)
Ergonomie der thermischen Umgebung - Analytische Bestimmung und Interpretation der
Wärmebelastung durch Berechnung der vorhergesagten Wärmebeanspruchung
(ISO/DIS 7933:2021)
Ergonomie des ambiances thermiques - Détermination analytique et interprétation de la
contrainte thermique fondées sur le calcul de l'astreinte thermique prévisible (ISO/DIS
7933:2021)
Ta slovenski standard je istoveten z: prEN ISO 7933
ICS:
13.180 Ergonomija Ergonomics
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT INTERNATIONAL STANDARD
ISO/DIS 7933.2
ISO/TC 159/SC 5 Secretariat: BSI
Voting begins on: Voting terminates on:
2021-11-12 2022-01-07
Ergonomics of the thermal environment — Analytical
determination and interpretation of heat stress using
calculation of the predicted heat strain
Ergonomie des ambiances thermiques — Détermination analytique et interprétation de la contrainte
thermique fondées sur le calcul de l'astreinte thermique prévisible
ICS: 13.180
This document is circulated as received from the committee secretariat.
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ISO/DIS 7933.2:2021(E)
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ISO/DIS 7933.2:2021(E)
© ISO 2021
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ii
ISO/DIS 7933.2:2021(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols . 2
5 Principles of the predicted heat strain (PHS) model . 4
6 Main steps of the calculation .5
6.1 Heat balance equation . 5
6.1.1 Metabolic rate, M . 5
6.1.2 Effective mechanical power, W . 5
6.1.3 Heat flow by respiratory convection, C . 5
res
6.1.4 Heat flow by respiratory evaporation, E . 5
res
6.1.5 Heat flow by conduction, K . 5
6.1.6 Heat flow by convection, C . 6
6.1.7 Heat flow by radiation, R . 6
6.1.8 Heat flow by evaporation, E . 6
6.1.9 Heat storage for increase of core temperature associated with the
metabolic rate, dS . 6
eq
6.1.10 Heat storage, S . 6
6.2 Calculation of the required evaporative heat flow, the required skin wettedness
and the required sweat rate . 7
7 Interpretation of required sweat rate . 7
7.1 Basis of the method of interpretation . 7
7.1.1 Stress criteria . 7
7.1.2 Strain criteria . 7
7.1.3 Reference values . 8
7.2 Analysis of the work situation . 8
7.3 Determination of allowable exposure time, D . 8
lim
Annex A (normative) Data necessary for the computation of thermal balance .9
Annex B (informative) Criteria for estimating acceptable exposure time in a hot work
environment .17
Annex C (informative) Metabolic rate .19
Annex D (informative) Clothing thermal characteristics .20
Annex E (informative) Computer programme for the computation of the predicted heat
strain model .22
Annex F (normative) Examples of the predicted heat strain model computations .27
Bibliography .28
iii
ISO/DIS 7933.2:2021(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
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electrotechnical standardization.
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described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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URL: www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 159, Ergonomics, Subcommittee SC 5,
Ergonomics of the physical environment.
This third edition supersedes the second edition (ISO 7933:2004), which has been technically revised.
The main changes compared to the previous edition are as follows:
— The maximum sweat rate SW described in section B.4 of Annex B is fixed; that is, it is no longer
max
adjusted for metabolic rate.
— As the model has not been extensively validated for conditions with unsteady environmental
parameters, metabolic rate and/or clothing, a caution was added for cases where these parameters
vary substantially with time.
iv
ISO/DIS 7933.2:2021(E)
Introduction
[1]
ISO 15265 describes the assessment strategy for the prevention of discomfort or health effects in
[2]
any thermal working condition, while ISO 16595/WP recommends specific practices concerning
hot working environments. For these hot environments, these standards propose to rely on the wet
[3]
bulb globe temperature (WBGT) heat stress index described in ISO 7243 as a screening method for
establishing the presence or absence of heat stress, and on the more elaborate method presented in this
document, to make a more accurate estimation of stress, to determine the allowable durations of work
in these conditions, and to optimize the methods of protection. This method, based on an analysis of the
heat exchange between a person and the environment, is intended to be used directly when it is desired
to carry out a detailed analysis of working conditions in heat.
This document makes it possible to predict the evolution of a few physiological parameters (skin and
rectal temperatures, as well as sweat rate) over time for a person working in a hot environment. This
prediction is made according to the climatic parameters, the energy expenditure of the person and his/
her clothing. This prediction is made for an average person and should be used to assess the risk of heat
stress for a group of people; and it cannot predict a particular person’s responses.
This document is based on the latest scientific information. Future improvements concerning the
calculation of the different terms of the heat balance equation, or its interpretation will be taken into
account in the future when they become available.
Occupational health specialists are responsible for evaluating the risk encountered by a given individual,
taking into consideration their specific characteristics that can differ from those of a standard person.
[4]
ISO 9886 describes how physiological parameters are used to monitor the physiological behaviour of
[5]
a particular person and ISO 12894 describes how medical supervision is organized.
v
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