EN ISO 7726:2025

SLOVENSKI STANDARD
01-februar-2026
Nadomešča:
SIST EN ISO 7726:2002
Ergonomija toplotnega okolja - Instrumenti za merjenje in spremljanje fizikalnih
veličin (ISO 7726:2025)
Ergonomics of the thermal environment - Instruments for measuring and monitoring
physical quantities (ISO 7726:2025)
Ergonomie der thermischen Umgebung - Instrumente zur Messung physikalischer
Größen (ISO 7726:2025)
Ergonomie des ambiances thermiques - Appareils de mesure des grandeurs physiques
(ISO 7726:2025)
Ta slovenski standard je istoveten z: EN ISO 7726:2025
ICS:
13.180 Ergonomija Ergonomics
17.020 Meroslovje in merjenje na Metrology and measurement
splošno in general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 7726
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2025
EUROPÄISCHE NORM
ICS 13.180 Supersedes EN ISO 7726:2001
English Version
Ergonomics of the thermal environment - Instruments for
measuring and monitoring physical quantities (ISO
7726:2025)
Ergonomie des ambiances thermiques - Appareils et Ergonomie der thermischen Umgebung - Instrumente
méthodes de mesure et de surveillance des grandeurs zur Messung und Überwachung physikalischer Größen
physiques (ISO 7726:2025) (ISO 7726:2025)
This European Standard was approved by CEN on 16 September 2025.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 7726:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 7726:2025) has been prepared by Technical Committee ISO/TC 159
"Ergonomics" in collaboration with Technical Committee CEN/TC 122 “Ergonomics” the secretariat of
which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by April 2026, and conflicting national standards shall be
withdrawn at the latest by April 2026.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 7726:2001.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 7726:2025 has been approved by CEN as EN ISO 7726:2025 without any modification.

International
Standard
ISO 7726
Third edition
Ergonomics of the thermal
2025-10
environment — Instruments for
measuring and monitoring physical
quantities
Ergonomie des ambiances thermiques — Appareils et méthodes
de mesure et de surveillance des grandeurs physiques
Reference number
ISO 7726:2025(en) © ISO 2025
ISO 7726:2025(en)
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 7726:2025(en)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviation . 1
5 General . 2
5.1 Specifications and methods .2
5.2 The heat exchanges between human body system and its environment .2
6 Physical quantities characterizing heat exchanges . 3
6.1 General .3
6.2 Basic physical quantities .3
6.2.1 Quantities .3
6.2.2 Air temperature .3
6.2.3 Radiation .3
6.2.4 Plane radiant temperature .4
6.2.5 Dew point temperature .4
6.2.6 Relative humidity .4
6.2.7 Surface temperature .4
6.2.8 Air velocity . . .4
6.2.9 Globe temperature .4
6.2.10 Psychrometric wet-bulb temperature .4
6.2.11 Natural wet-bulb temperature .4
6.3 Derived physical quantities .5
6.3.1 General .5
6.3.2 Mean radiant temperature .5
6.3.3 Radiant temperature asymmetry .5
6.3.4 Operative temperature .5
6.3.5 Water vapour partial pressure .6
6.3.6 Humidity ratio .6
6.3.7 Turbulence intensity .6
7 The characteristics of physical quantity measuring instruments . 6
7.1 General .6
7.2 Characteristics of instruments for measuring the basic quantities .6
7.3 Characteristics of integrating types of measuring instruments .8
8 Specifications relating to measuring methods . 9
8.1 General .9
8.2 Specifications relating to variations in the physical quantities within the space
surrounding the subject .9
8.3 Specifications relating to the variations in the physical quantities with time .10
9 Specifications relating to monitoring methods .11
10 Measurement uncertainty .11
11 Specifications related to the processing of measurement results .11
11.1 Spatial maps of measured data . 12
Annex A (informative) Measurement of air temperature .13
Annex B (informative) Measurement and calculation of the mean radiant temperature .15
Annex C (informative) Measurement of plane radiant temperature .26
Annex D (informative) Measurement of the absolute humidity of the air .32

iii
ISO 7726:2025(en)
Annex E (informative) Measurement of air velocity .39
Annex F (informative) Measurement of surface temperature .42
Annex G (informative) Measurement of operative temperature .44
Annex H (informative) Measurement of the natural wet-bulb temperature .46
Bibliography .48

iv
ISO 7726:2025(en)
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 through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see 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, in collaboration with the European Committee for Standardization
(CEN) Technical Committee CEN/TC 122, Ergonomics, in accordance with the Agreement on technical
cooperation between ISO and CEN (Vienna Agreement).
This third edition cancels and replaces the second edition (ISO 7726:1998), which has been technically
revised.
The main changes are as follows:
— the physical quantities characterizing heat exchanges between a system and its environment have been
divided into basic and derived. The basic quantities (like air temperature, irradiation and plane radiant
temperature) are measured directly, while the derived quantities (like mean radiant temperature,
operative temperature, humidity ratio, etc.) are measured indirectly (see 6.1 and 6.2);
— the concept of measurement uncertainty has been introduced (see Clause 11).
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

v
ISO 7726:2025(en)
Introduction
This document is one of a group of International Standards on the ergonomics of the thermal environment
intended for use in the study of thermal environments.
This group of International Standards covers:
— definitions for the terms to be used in the methods of measurement, testing or interpretation, taking into
account standards already in existence or in the process of being drafted;
— the laying down of specifications relating to the methods for measuring the physical quantities which
characterize thermal environments;
— the selection of one or more methods for interpreting the parameters;
— the specification of recommended values or limits of exposure for the thermal environments coming
within the comfort range and for extreme environments (both hot and cold);
— the specification of methods for measuring the efficiency of devices or processes for personal or collective
protection from heat or cold.
The aim of this group of standards is simply to standardize the process of recording information leading to
the determination of values of physical quantities. Other International Standards give details of the methods
that make use of the information obtained in accordance with this standard.
This document can be used as a reference when establishing:
a) specifications for manufacturers and users of instruments for measuring the physical quantities of the
environment;
b) a written contract between two parties for the measurement of these quantities.
It applies to the influence of hot, moderate, comfortable or cold environments on people. This document is
applied in cases wherein comfort or human strain are the main concern.
Any measuring instrument which achieves the accuracy indicated in this document may be used. The
description or listing of certain instruments in the annexes only signifies that they are "recommended",
since characteristics of these instruments can vary according to the measuring principle, their construction
and the way in which they are used. It is up to users to compare the quality of the instruments available
on the market at any given moment and to check that they conform to the specifications contained in this
document.
vi
International Standard ISO 7726:2025(en)
Ergonomics of the thermal environment — Instruments for
measuring and monitoring physical quantities
1 Scope
This document specifies the minimum characteristics of instruments for measuring physical quantities
characterizing an environment, as well as the methods for measuring the physical quantities of this
environment.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 13731, Ergonomics of the thermal environment — Vocabulary and symbols
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 13731 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Symbols and abbreviation
For the purposes of this document, the symbols and units listed in Table 1 apply.
Table 1 — Symbols and units
Symbol Term Unit
A surface area projected on one direction m
pr
A total radiant surface area m
r
-2
C convective heat flow W·m
-2
C respiratory convective heat flow W·m
res
-2
E evaporative heat flow at the skin W·m
-2
E respiratory evaporative heat flow W·m
res
-2
K conductive heat flow W·m
-2
M metabolic rate W·m
p atmospheric pressure Pa
p water vapour partial pressure Pa
a
p saturated water vapour pressure Pa
as
p saturated water vapour pressure at the wet-bulb temperature Pa
as,w
-2
R radiative heat flow W·m
R relative humidity %
h
ISO 7726:2025(en)
TTabablele 1 1 ((ccoonnttiinnueuedd))
Symbol Term Unit
-2
S body heat storage rate W·m
t air temperature °C or K
a
t dew-point temperature °C or K
d
t globe temperature °C or K
g
t natural wet-bulb temperature °C or K
nw
t operative temperature °C or K
o
t plane radiant temperature °C or K
pr
__
mean radiant temperature °C or K
tT,
r,
r
t surface temperature °C or K
s
t psychrometric wet-bulb temperature °C or K
w
-1
v air velocity m·s
a
-2
W effective mechanical power W·m
-1
W humidity ratio g·kg
a
5 General
5.1 Specifications and methods
The specifications and methods contained in this document have been divided into two classes according
to the extent of the thermal annoyance to be assessed. The type C specifications and methods relate to
measurements carried out in moderate environments. The type S specifications and methods relate to
measurements carried out in severe environments.
The specifications and methods described for each of these classes have been determined bearing in mind
the practical possibilities of in situ measurements and monitoring and the performances of measuring
instruments available at present.
Instructions are provided for monitoring (how, where, when) and for post processing recorded data.
5.2 The heat exchanges between human body system and its environment
The energy balance on the human body is shown in Formula (1):
SM=−()WR±±CE±±EC±±K (1)
resres
This balance expresses that the internal heat production of the body, which corresponds to the metabolic
rate, M, minus the effective mechanical power, W, are balanced by the heat exchanges in the respiratory
tract by convection, C , and evaporation, E , as well as by the heat exchanges on the skin by conduction, K,
res res
convection, C, radiation, R, and evaporation, E.
Each term in Formula (1) requires the knowledge of some physical quantities. In Table 2, these quantities
and their connections with energy balance on a human body are shown.

ISO 7726:2025(en)
Table 2 — Main independent quantities
Elements in thermal balance Air tempera- Mean radiant Surface tem- Air ve- Water vapour
ture temperature perature locity partial pressure
t t t v p
a r s a a
Heat transfer by radiation, R X X
a
Heat transfer by convection, C X X
Heat exchanges through evapora- X X
tion:
—  evaporation from the skin, E
—  evaporation by respiration, E
res
Convection by respiration, C X
res
Heat transfer by conduction, K X
a
Heat transfer by convection is also affected by body movements. The resultant air velocity at skin level is usually defined
relative air velocity (v ).
ar
6 Physical quantities characterizing heat exchanges
6.1 General
In general, the quantities affecting the energy balance on a system can be divided into two categories, basic
and derived, depending to the possibility to measure them directly or indirectly.
6.2 Basic physical quantities
6.2.1 Quantities
The basic physical quantities are the quantities directly measurable. These quantities are as follows:
— air temperature;
— radiation flux;
— plane radiant temperature;
— dew point temperature;
— relative humidity;
— air velocity;
— surface temperature;
— globe temperature;
— psychrometric wet-bulb temperature;
— natural wet-bulb temperature.
6.2.2 Air temperature
It is the temperature of the air around the human body. It is measured by a temperature sensor shielded
against radiation (see Annex A).
6.2.3 Radiation
It is the energy exchanged by radiation from system and its environment. It is measured by a radiometer
(see Annex C).
ISO 7726:2025(en)
6.2.4 Plane radiant temperature
It is the uniform temperature of an enclosure where the irradiance on one side of a small plane element is
the same as in the non-uniform actual environment. It can be measured from radiation with a radiometer
or calculated from the surface temperatures of the environment and the shape factors between the surfaces
and the plane element (see Annex C).
6.2.5 Dew point temperature
It is the temperature at which air becomes saturated (100 % relative humidity) with water vapour when
cooled at constant pressure. In other words, the water vapor partial pressure at the given temperature is
equal to the saturated water vapor pressure at the dew-point temperature (see Annex D).
6.2.6 Relative humidity
It is the actual vapour pressure divided by vapour pressure at saturation at the same temperature. It is
measured by a capacitance hygrometer or a hair absorption hygrometer (see Annex D).
6.2.7 Surface temperature
It is the temperature of a given surface. It is measured by contact thermometers (resistance, thermocouples)
or infrared sensors (see Annex F).
6.2.8 Air velocity
It is average velocity of the air, i.e. the magnitude of the velocity vector of the flow at the measuring point
considered, over an interval of time (measuring period). It is measured using an anemometer (see Annex E).
6.2.9 Globe temperature
It is the temperature measured from a black-globe thermometer consisting of a black globe in the centre of
which is placed a temperature sensor such as an expansion thermometer, a thermocouple or a resistance
probe (see Annex B).
6.2.10 Psychrometric wet-bulb temperature
It is the temperature indicated by a psychrometer when the bulb of one thermometer is covered with a water
saturated wick over which air is caused to flow at approximately 4,5 m/s to reach an equilibrium temperature
of water evaporating into air, when the heat of vaporization is supplied by the sensible heat of the air. This
temperature is lower than that of the gas stream itself and is the dynamic equilibrium value attained when
the convective heat transfer to the sensor effectively equals the evaporative heat load associated with the
moisture loss from the wetted surface. If small corrections are applied to a wet-bulb thermometer (e.g. a gas
-1
stream velocity greater than 3 m·s ), it returns with a good approximation of the thermodynamic wet-bulb
temperature. This is the limiting temperature reached as a gas cools on adiabatic saturation and is more
properly termed the adiabatic-saturation temperature to avoid confusion. It is measured by a psychrometer
(see Annex D).
6.2.11 Natural wet-bulb temperature
It is the temperature value read by a sensor covered with a wetted wick that is ventilated naturally (i.e.
placed in the environment under consideration without additional forced ventilation). Since the sensor is
unshielded, this quantity is affected also by radiation and cannot be confused with the psychrometric wet-
bulb temperature. It is measured by a natural wet-bulb temperature sensor (see Annex H).

ISO 7726:2025(en)
6.3 Derived physical quantities
6.3.1 General
The derived physical quantities are calculated from basic ones, or represent or characterize a group
of factors of the environment, weighted according to the characteristics of the sensors used. The second
ones are often used to define an empirical index of comfort or thermal stress without having recourse to a
rational method based on estimates of the various forms of heat exchanges between the human body and
the thermal environments, and of the resulting thermal balance and physiological strain. The following
derived quantities are described in the specific standards as they apply and where measuring requirements
are included:
— mean radiant temperature;
— radiant temperature asymmetry;
— operative temperature;
— water vapour partial pressure;
— humidity ratio;
— turbulence.
6.3.2 Mean radiant temperature
It is the uniform temperature of an imaginary enclosure in which radiant heat transfer from the human
body is equal to the radiant heat transfer in the actual non-uniform enclosure.
The mean radiant temperature can be calculated from quantities measured by instruments which allow the
generally heterogeneous radiation from the walls of an actual enclosure to be "integrated" into a mean value
(see Annex B).
The mean radiant temperature can also be calculated from measured values of the temperature of the
surrounding walls and the size of these walls and their position in relation to a person (see Annex B).
The mean radiant temperature may also be calculated from the plane radiant temperature in six opposite
directions weighted according to the projected area factors for a person. Similarly, it can be estimated from
the measurement of the radiant flux from different directions (see Annex B).
6.3.3 Radiant temperature asymmetry
The radiant temperature asymmetry is the difference between the plane radiant temperature of the two
opposite sides of a small plane element (see 5.1.3).
The asymmetric radiant field is defined in relation to the position of the plane element used as a reference.
It is, however, necessary to specify exactly the position of the latter by means of the direction of the normal
to this element.
The radiant temperature asymmetry is measured or calculated from the measured value of the plane radiant
temperature in the two opposing directions (see Annex C).
6.3.4 Operative temperature
The operative temperature is the uniform temperature of an imaginary black enclosure in which an
occupant would exchange the same amount of heat by radiation plus convection as in the actual non-
uniform environment. It is measured or calculated from air temperature and mean radiant temperature (see
Annex G).
ISO 7726:2025(en)
6.3.5 Water vapour partial pressure
It is the pressure which the water vapour would exert if it alone occupied the whole volume occupied by the
mixture at the same temperature. It is proportional to the absolute humidity, which represents to the actual
amount of water vapour contained in the air as opposed to quantities such as the relative humidity or the
saturation level.
The water vapour partial pressure can be determined directly or indirectly (see Annex D).
6.3.6 Humidity ratio
It is the ratio of the mass of water vapor in a sample of ambient air to the mass of dry air in the same sample
(see Annex D).
6.3.7 Turbulence intensity
It is the standard deviation of the local air velocity to the local mean air velocity.
7 The characteristics of physical quantity measuring instruments
7.1 General
The characteristics depend on the class (C and S).
7.2 Characteristics of instruments for measuring the basic quantities
When a measurement is carried out, it is necessary to differentiate between the accuracy of the physical
quantity that is affected by the variables involved in the measuring operations (e.g. the position of the
sensors) and the accuracy of the sensor. To obtain reliable results, the former is the most important.
The measuring ranges, the measuring accuracy of the sensors for measuring the basic quantities are
summarized in Table 3. These characteristics shall be considered to be minimum requirements for each
class (C and S). That means that according to needs and technical manufacturing possibilities, it is always
possible to specify more exact characteristics or more prescriptive values. For certain quantities, very
precise thermal stress measurements can require the use of appliances with measuring ranges in class S and
accuracy of class C. The characteristics of measuring instruments for basic physical quantities are specified
in Table 4 (classes C and S). They shall be used as a reference, except where this contradicts the principle
for measuring the quantities under consideration. In any case it is important to consider instrumental
measurement uncertainty and measuring chain uncertainty (see Clause 8).
For the purposes of this document, the time constant of a sensor is considered to be numerically equal to
the time taken for the output of the sensor, in response to a step change in the environmental quantity being
measured, to reach 63 % of its final change in steady-state value without overshoot. The response time,
which is in practice the time after which the quantity being measured (for example: temperature of the
thermometer) can be considered to be sufficiently close to the exact figure for the quantity to be measured
(for example: temperature of the air), can be calculated from the time constant. A 90 % response time is
achieved after a period equal to 2,3 times the time constant. It is necessary to wait, as a minimum, for a
time equivalent to the response time before a measurement is taken. In Table 4 the standard environmental
conditions for the determination of time constants of sensors are reported.
As the time constant of a sensor does not depend solely on the sensor (mass, surface area, presence of a
protective shield) but also on the environment, and hence on factors connected with a given measurement
(air velocity, radiation, etc.), it is necessary to indicate the conditions under which these values were
obtained.
All measurement instruments should be periodically calibrated and verified they satisfy all required
specifications.
ISO 7726:2025(en)
Table 3 — Characteristics of measuring instruments for basic physical quantities
Class C (comfort) Class S (stress) Comments
Quantity Sym- Measur- Accuracy Response Measur- Accuracy Response
bol ing range time ing range time
Air tempera- t 10 °C to Required: ≤ 1 min -60 °C to Required: ≤ 1 min Response
a
ture 35 °C ±(0,3 °C + 150 °C ±(0,6 °C + time takes
0,005∙|t | °C) 0,01∙|t | °C) into account
a a
that the
Desirable: Desirable:
measure-
±(0,1 °C ±(0,15 °C +
ment is
+ 0,001 0,002∙|t | °C)
a
carried out
7∙|t | °C)
a
in air.
-2 -2
Radiation flux r -35 W∙m Required: ≤ 1 min -300 W∙m Required: 10 % ≤ 1 min Accuracy
d
-2
-2
to ±5 W∙m to -100 values
±5 W∙m
-2 -2
35 W∙m W∙m have been
Desirable:
10 %
-2 -2
chosen as a
spectral ±5 W∙m -100 W∙m
Desirable:
function of
range: to +100
5 %
-2
the different
0,3 µm to W∙m
-2
±5 W∙m
measuring
50 µm
> +100
ranges and
-2 5 %
W∙m
propor-
spectral
tional to
range:
the read
0,3 µm to
value in
50 µm
the ranges
-2
300 W∙m
to
-2
-100 W∙m
and >
-2
+100 W∙m .
Plane radiant t 0 °C to Required: -60 °C to Required:
pr
temperature 50 °C ±(0,6 °C + +200 °C ±(1,2 °C +
0,05∙|t | °C) 0,02∙|t | °C)
pr pr
Desirable: Desirable:
±(0,2 °C + ±(0,6 °C +
0,04∙|t | °C) 0,02∙|t | °C)
pr pr
These levels These levels
shall be shall be guar-
guaranteed anteed at least
at least for a for a deviation
deviation |t - |t -t |
pr pr a
t | < 10 °C
< 50 °C
a
Dew point t -5 °C to Required: -5 °C to Required:
d
temperature 28 °C 0,2 °C +50 °C 0,5 °C
Desirable: Desirable:
0,1 °C 0,2 °C
Relative hu- R 20 % to Required: 3 % ≤ 3 min 5 % to Required: 3 % ≤ 3 min The range
h
midity 80 % 95 % proposed
Desirable: Desirable: 2 %
for class S
10 °C to 2 %
instruments
35 °C
is consistent
with the
limits of
the current
measure-
ment tech-
nology.
ISO 7726:2025(en)
TTabablele 3 3 ((ccoonnttiinnueuedd))
Class C (comfort) Class S (stress) Comments
Quantity Sym- Measur- Accuracy Response Measur- Accuracy Response
bol ing range time ing range time
Surface tem- t 0 °C to Required: ≤ 1 min -50 °C to Required: ≤ 1 min The accu-
s
perature 50 °C ±(0,6 °C + +200 °C ±(0,6 °C + racy of the
0,01∙|t | °C) 0,01∙|t |°C) measure-
s s
ment is
Desirable: Desirable:
affected by
±(0,15 °C + ±(0,15 °C +
the contact
0,002∙|t |°C) 0,002∙|t |°C)
s s
pressure.
-1 -1
Air velocity v 0,05 m∙s Required: Required: 0,1 m∙s Required: ±(0,1 Required: The turbu-
a
-1 -1
to 1 m∙s ±(0,1 + ≤ 2 s to + 0,05∙v ) m∙s ≤ 2 s lence inten-
a
-1
-1
0,05∙v ) m∙s sity can be
Desirable: 20 m∙s Desirable: ±(0,1 Desidera-
a
-1
calculated
Desirable: ≤ 1 s + 0,03∙v ) m∙s ble: ≤ 1 s
a
only with
±(0,05 +
For tur- For tur-
-1
a suitable
0,05∙v ) m∙s
bulence bulence
a
frequency
These levels measure- measure-
of the meas-
shall be ment ment
urement.
guaranteed
≤ 0,2 s ≤ 0,2 s
The ranges
whatever
(*) (*)
of air veloci-
the direction
ty are made
of air flow
consistent
within a solid
with the
angle ω
accuracies
= 3π sr
specified.
Globe temper- t 0 °C to Required: ≤ 30 min -50 °C to Required: ≤ 30 min for a globe
g
ature 50 °C ±(0,6 °C + +200 °C ±(0,6 °C + 150 mm in
0,01∙|t |°C) 0,01∙|t |°C) diameter.
g g
Desirable: Desirable:
±(0,15 °C +  ±(0,15 °C +
0,002∙|t |°C) 0,002∙|t |°C)
g g
Psychromet- t 5 °C to Required: ≤ 1 min - - - Response
w
ric wet-bulb 40 °C ±(0,6 °C + time takes
temperature 0,01∙|t | °C) into account
w
that the
Desirable:
measure-
±(0,15 °C +
ment is
0,002∙|t | °C)
w
carried out
in air.
Natural wet- t - - 5 °C to Required: ≤ 1 min Response
nw
bulb temper- 40 °C ±(0,6 °C + time takes
ature 0,01∙|t | °C) into account
nw
that the
Desirable:
measure-
±(0,15 °C +
ment is
0,002∙|t | °C)
nw
carried out
in air.
7.3 Characteristics of integrating types of measuring instruments
All measurement instruments should be periodically calibrated and verified they satisfy all required
specifications.
Any measuring instrument integrating the measurement of several variables (e.g. WBGT index meters)
shall have a measuring interval, and an accuracy equal to or better than those of the minimum between
corresponding individual variables.

ISO 7726:2025(en)
All measurement instruments should be periodically calibrated and verified they satisfy all required
specifications.
8 Specifications relating to measuring methods
8.1 General
The methods for measuring the physical quantities characterizing the environment shall take account of
the fact that these characteristics vary in location and time. Furthermore, the methods can be different
depending on the environment use, for example for human occupation or for the collections preservation. In
this document, only environments for human occupation are considered.
Table 4 — Standard environmental conditions for the determination of time constants of sensors
_
t p v
a a a
t
r
-1
Air temperature = t any < 0,15 m·s
a
-1
_
Mean radiant temperature = t any < 0,15 m·s
a
= t
r
-1
Plane radiant temperature = 20 °C = t any < 0,15 m·s
a
Water vapour partial pres- = 20 °C = t To be specified according
a
sure
to the measuring method
Air velocity = 20 °C = t any -
a
-1
Surface temperature = 20 °C = t any < 0,15 m·s
a
The thermal environment can vary with time and the horizontal location and the vertical direction (as
shown in 8.2). Therefore, it should be taken into account for how long a time a person is working at the
different locations.
8.2 Specifications relating to variations in the physical quantities within the space
surrounding the subject
It is first necessary to check whether the environment is homogeneous or heterogeneous
An environment should be considered to be "homogeneous" from the microclimatic point of view if, at a
given moment, air temperature, globe temperature, mean radiant temperature, air velocity and relative
humidity can be considered to be practically uniform around the subject, i.e. when the deviations between
each of these quantities and their mean spatial value calculated as a mean of the locations does not exceed
the values obtained by multiplying the required measuring accuracy from Table 3 by the corresponding
factor X listed in Table 5. This condition is frequently met in case of air temperature, air velocity and relative
humidity, but more rarely in the case of mean radiant temperature. If the environment is homogeneous, the
arithmetic mean of values of physical quantities is not required.
When the environment is heterogeneous, the physical quantities shall be measured at several locations at or
around the subject or in a position representative of the occupation and account taken of the partial results
obtained in order to determine the mean value of the quantities to be considered in assessing the comfort
or the thermal stress. Other standards in this group, such as ISO 15265 or ISO 15743, provide information
about the previous analyses of the comfort or the thermal stress conditions of the workplaces being studied
or of workplaces of a similar type can provide information of interest in determini
...