ISO standards in the area of the Ergonomics of the Physical Environment

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. Ken Parsons, Chair ISO TC159 SC5 ‘Ergonomics of the Physical Environment’ Emeritus Professor of Environmental Ergonomics, Loughborough University, UK

Introduction

International standards for the design and assessment of physical environments are produced by ISO TC159 SC5 and other ISO committees. It can be considered that all of the standards lead to the design of the physical environment for people. The system of standards for cold stress, thermal comfort and heat stress are provided in figures 1, 2 and 3 and are represented in integrated form in figure 4. As well as contributing to thermal environments, clothing (see also ISO TC94 SC13), metabolic rate (related to energy and fatigue) and overall risk assessment strategy are relevant to physical environments (ISO 9920, ISO 8996 and ISO 15265). ISO 10551 and ISO 28802 describe subjective scales and the environmental survey which allow direct assessment of physical environments. ISO 13732 parts 1 to 3 describes skin reaction to contact with surfaces and may have application beyond the design of thermal conditions. The ergonomics of lighting is considered in ISO 8995 and has been taken over by ISO TC 274. ISO 28803 provides best available information on how to apply standards for people with special requirements (populations beyond the scope of existing standards). Accessibility standards (ISO 24500’ series) cover specific aspects of accessibility to physical environments. A series of standards is concerned with signals and communication in noisy environments and complements standards produced by other ISO committees (e.g. ISO TC43 SC1; ISO TC108 SC4). Work on the perception of air quality was transferred to ISO TC146. ISO 15742 will provide methods for considering total environments and how different environmental components combine to provide overall human response. ISO 11399 provides an overview of the system of standards and ISO 13731 provides definitions of terms used in standards.

ISO standards for the assessment of cold stress The principle ISO standard for the assessment of people in cold conditions is ISO 11079 which uses measures of air temperature, radiant temperature, air velocity and humidity along with metabolic rate and clothing insulation, to calculate the Required Clothing Insulation cold stress index (IREQ). This index indicates the clothing people should wear in cold conditions. The input parameters described above can be obtained from ISO 9920, ISO 8996 and ISO 7726. Using an IREQ value, clothing can be selected from a database of clothing insulation values provided in ISO 9920. For a given clothing insulation (e.g. where only actual clothing worn is available) ISO 11079 suggests limit times for exposure to cold. The standard also provides an indication of the effects of wind chill and danger, for example, to exposed skin (e.g. risk of frostbite). ISO 12894 provides a method for screening people to determine whether it is appropriate to expose them to cold. ISO 13732-3 determines skin reaction on contact with cold surfaces and ISO 9886 describes a method of direct measurement of cold strain using physiological methods. ISO 15265 provides an overall strategy for assessing a thermal environment and all of the standards are brought together in a process standard (ISO 15743) which describes how to design and manage cold environments. In each case it briefly explains the purpose of each standard and, with the aid of block diagrams, shows how the various standards are inter-related.

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Figure 1 : The system of ISO standards for the assessment of cold stress

ISO standards for the assessment of thermal comfort

The principle ISO standard for the assessment of thermal comfort is ISO 7730 which uses measures of air temperature, radiant temperature, air velocity and humidity along with metabolic rate and clothing insulation, to calculate the Predicted Mean Vote (PMV) thermal comfort index which is a value between +3,hot and -3,cold. A value of 0 is neutral and optimum for comfort. The PMV predicts the average value that a large group of people would rate on the scale, if they were exposed to the conditions under consideration. The Predicted Percentage of Dissatisfied (PPD) in those conditions is also provided. The input parameters described above can be obtained from ISO 9920, ISO 8996 and ISO 7726. ISO 10551 provides guidance on how to construct subjective scales for the direct measurement of comfort. Standards are also available for assessment of vehicle environments and for predicting how skin contact with surfaces will feel. ISO 15265 provides an overall strategy for assessing a thermal environment and all of the standards are brought together in a process standard (ISO 16594) which describes how to design thermal environments for thermal comfort.


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Figure 2: The system of ISO standards for the assessment of thermal comfort


ISO standards for the assessment of Heat stress

The principle ISO standards for the assessment of people in hot conditions are ISO 7243 and ISO 7933. ISO 7243 is a screening method based upon the wet bulb globe temperature index (WBGT). If the measured value is above a limit value then unacceptable heat strain may occur and action is required. If it is below the limit value the conditions are acceptable. ISO 7933 uses measures of air temperature, radiant temperature, air velocity and humidity along with metabolic rate and clothing insulation in the Predicted Heat Strain method (PHS). It involves the calculation of the amount of sweat required to lose sufficient heat from a person and along with other criteria, including dehydration, provides a method of interpretation in terms of likely physiological response and suggested limits in terms of exposure times. The input parameters described above can be obtained from ISO 9920, ISO 8996 and ISO 7726. ISO 12894 provides a method for screening people to determine whether it is appropriate to expose them to heat. ISO 13732-1 determines skin reaction on contact with hot surfaces (burns) and ISO 9886 describes a method of direct measurement of heat strain using physiological methods. ISO 15265 provides an overall strategy for assessing a thermal environment and all of the standards are brought together in a process standard (ISO 16595) which describes how to design and manage hot environments.


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Figure 3 : The system of ISO standards for the assessment of heat stress


ISO standards for the design and assessment of Physical environments

Finally, these ISO standards for the assessment of differing thermal environments are part of a larger assembly of Standards concerning the overall physical environment. The relationships and connections between these different documents are summarized in Figure 4. Collectively they represent a growing source of guidance and evaluative criteria to assist in the assessment of such environments from an ergonomics perspective.


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Figure 4 : The system of ISO standards for the Ergonomics of the physical environment.

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