ISO/TC 159/SC 5/WG 1 - Thermal environments

ISO 7243:2017 presents a screening method for evaluating the heat stress to which a person is exposed and for establishing the presence or absence of heat stress. It applies to the evaluation of the effect of heat on a person during his or her total exposure over the working day (up to 8 h). It does not apply for very short exposures to heat. It applies to the assessment of indoor and outdoor occupational environments as well as to other types of environment, and to male and female adults who are fit for work.

ISO 11079:2007specifies methods and strategies for assessing the thermal stress associated with exposure to cold environments. These methods apply to continuous, intermittent as well as occasional exposure and type of work, indoors and outdoors. They are not applicable to specific effects associated with certain meteorological phenomena (e.g. precipitation), which are assessed by other methods.

ISO 9920:2007 specifies methods for estimating the thermal characteristics (resistance to dry heat loss and evaporative heat loss) in steady-state conditions for a clothing ensemble based on values for known garments, ensembles and textiles. It examines the influence of body movement and air penetration on the thermal insulation and water vapour resistance. It does not deal with other effects of clothing, such as adsorption of water, buffering or tactile comfort, take into account the influence of rain and snow on the thermal characteristics, consider special protective clothing (water-cooled suits, ventilated suits, heated clothing), or deal with the separate insulation on different parts of the body and discomfort due to the asymmetry of a clothing ensemble.

ISO 7730:2005 presents methods for predicting the general thermal sensation and degree of discomfort (thermal dissatisfaction) of people exposed to moderate thermal environments. It enables the analytical determination and interpretation of thermal comfort using calculation of PMV (predicted mean vote) and PPD (predicted percentage of dissatisfied) and local thermal comfort, giving the environmental conditions considered acceptable for general thermal comfort as well as those representing local discomfort.

The metabolic rate, as a conversion of chemical into mechanical and thermal energy, measures the energetic cost of muscular load and gives a numerical index of activity. Metabolic rate is an important determinant of the comfort or the strain resulting from exposure to a thermal environment. In particular, in hot climates, the high levels of metabolic heat production associated with muscular work aggravate heat stress, as large amounts of heat need to be dissipated, mostly by sweat evaporation. ISO 8996:2004 specifies different methods for the determination of metabolic rate in the context of ergonomics of the climatic working environment. It can also be used for other applications -- for example, the assessment of working practices, the energetic cost of specific jobs or sport activities, the total cost of an activity, etc.

ISO 7933:2004 specifies a method for the analytical evaluation and interpretation of the thermal stress experienced by a subject in a hot environment. It describes a method for predicting the sweat rate and the internal core temperature that the human body will develop in response to the working conditions. The various terms used in this prediction model, and in particular in the heat balance, show the influence of the different physical parameters of the environment on the thermal stress experienced by the subject. In this way, this International Standard makes it possible to determine which parameter or group of parameters should be modified, and to what extent, in order to reduce the risk of physiological strains. The main objectives of ISO 7933:2004 are the following: the evaluation of the thermal stress in conditions likely to lead to excessive core temperature increase or water loss for the standard subject; the determination of exposure times with which the physiological strain is acceptable (no physical damage is to be expected). In the context of this prediction mode, these exposure times are called "maximum allowable exposure times". ISO 7933:2004 does not predict the physiological response of individual subjects, but only considers standard subjects in good health and fit for the work they perform. It is therefore intended to be used by ergonomists, industrial hygienists, etc., to evaluate working conditions.

ISO 9886:2004 describes methods for measuring and interpreting the following physiological parameters: body core temperature; skin temperatures; heart rate; body-mass loss.

Purpose is to specify information which will allow the correct, effective and practical use of International Standards concerned with the ergonomics of the thermal environment. Describes the underlying principles concerning the ergonomics of the thermal environment.

Covers the construction and use of judgement scales for use in providing reliable and comparative data on the subjective aspects of thermal comfort or thermal stress.

Gives methods for estimating the thermal characteristics (resistance to dry heat loss and evaporative heat loss) in steady-state conditions for a clothing ensemble based on values for known garments, ensembles and textiles. Does not deal with other effects of clothing, such as adsorption of water, buffering, tactile comfort. Does not take into account the influence of rain and snow on the thermal characteristics. Does not consider special protective clothing. Does not deal with the separate insulation on different parts of the body and discomfort due to the asymmetry of a clothing ensemble.

The purpose is to present a method for predicting the thermal sensation and the degree of discomfort (thermal dissatisfaction) of people exposed to moderate thermal environments and to specify acceptable environmental conditions for comfort. Applies to healthy men and women and was originally based on studies of North American and European subjects but agrees also well with recent studies of Japanese subjects and is expected to apply with good approximation in most parts of the world. Applies to people exposed to indoor environments where the aim is to attain thermal comfort, or indoor environments where moderate deviations from comfort occur.

Proposes methods and strategies to assess the thermal stress associated with exposure to cold environments. Cold stress is suggested to be evaluated in terms of both general cooling of the body and local cooling of particular parts of the body (e.g. extremities and face). The methods apply to continuous, intermittent and occasional exposure and in both indoor and outdoor work. Specific effects associated with certain meteorological phenomena (e.g. precipitation) are not covered and should be assessed by other methods.

Describes methods for measuring and interpreting body core temperature, skin temperature, heart rate, and body mass loss. Annex A presents a comparison of the different methods concerning their field of application, their technical complexity, the discomfort and the risks. The measurement techniques are described in annex B, limit values are proposed in annex C.

Specifies methods for determining the metabolic rate, but can also be used for other applications, e.g. for the assessment of working practices, the cost of specific jobs or sport activities, the total cost of activity, etc. Annexes A to G contain: classification of metabolic rate for kinds of activities, classification of metabolic rate by occupation, data for standard person, metabolic rate for body posture, type of work and body motion related to work speed, metabolic rate for typical activities, example of calculation of the average metabolic rate for a work cycle, examples of calculation of the metabolic rate based on measured data.

Gives a method, which can easily be used in an industrial environment for evaluating the stresses on a individual. It applies to the evaluation of the mean effect of heat on man during a period representative of his activity but it does not apply to very short periods, nor to zones of comfort.

Describes a method of calculating the heat balances as well as the sweat rate that the human body should produce to maintain this balance in equilibrium. The various terms used show the influence of the different physical parameters. It does not predict the physiological response of individual subjects, but only considers standard subjects in good health and fit for the work they perform.