GBZ/T 229.3-2010Classification of occupational hazards at workplaces Part 3:Occupational exposure to heat stress (English PDF)

3.1 heat strain

The systemic physiological response caused by heat stress.

3.2 heat balance

The state in which the body, by regulating its rate of heat production and rate of heat dissipation, makes the heat produced equal to the heat dissipated, so that body temperature is kept in balance.

3.3 heat adaptation

The physiological adaptation process of increased heat tolerance of the body produced by long-term stimulation by a hot environment.

3.4 heat acclimatization

The physiological adaptation process in which an individual's ability to withstand heat intensity is progressively strengthened.

3.5 wet-bulb globe temperature index

Also called the WBGT index; a basic parameter for the comprehensive evaluation of the heat load of the working environment to which the human body is exposed.

Outdoor WBGT = natural wet-bulb temperature (°C) x 0.7 + globe temperature (°C) x 0.2 + dry-bulb temperature (°C) x 0.1

Indoor WBGT = natural wet-bulb temperature (°C) x 0.7 + globe temperature (°C) x 0.3

3.6 environment heat intensity

The intensity with which the temperature, humidity, air velocity and thermal radiation of the environment affect heat dissipation of the human body, expressed by the WBGT index.

3.7 clothing thermal insulation

The property of the clothing worn by workers during production work that affects heat dissipation of the human body, in units of Clo.

3.8 work-rest regimen

The work and rest schedule per unit time (hour) of work in hot environments established to prevent heat injury.

4.1 Classification principles and basic requirements

4.1.1 Classification shall be carried out on the basis of a comprehensive evaluation of the health hazards of the work in hot environments, the environment heat intensity, the duration of exposure to heat, the work intensity and the thermal insulation of the work clothing.

4.1.2 Before classification, the generating processes and distribution of heat at the workplace and the control and protective measures taken shall be identified through on-site inspection, data on previous heat injuries and accidents shall be collected, and the work to be classified shall be determined. Work classification shall be combined with routine monitoring.

4.1.3 The classification results and the effectiveness of the preventive and control measures shall be evaluated periodically. Where the evaluation results indicate a possible inconsistency with the original classification results, or where the production process, raw materials, equipment, etc. change, the work shall be reclassified and new preventive and control measures and recommendations shall be put forward.

4.1.4 The classification results are presented in the form of a classification report. The content of the report includes the basis of classification, the classification results, the preventive and control measures and recommendations, the method of effectiveness evaluation, and the parties that shall be informed.

4.1.5 The employer's responsible person, the managers and the workers concerned shall be informed of the classification report.

4.1.6 The classification data shall be archived.

4.2 Basis and method of classification

The basis for classifying work in hot environments includes the work intensity, the duration of exposure to work in hot environments, the WBGT index and the thermal insulation of the clothing.

4.2.1 When classifying work in hot environments, the class of physical work intensity shall be determined. The classification of physical work intensity shall be carried out in accordance with GBZ/T 189.10.

4.2.2 When classifying work in hot environments, the duration of exposure to work in hot environments shall be determined. It is calculated as the cumulative time of exposure to work in hot environments per working day, in minutes (min).

4.2.3 When classifying work in hot environments, the environment heat intensity of the work, i.e. the WBGT index, shall be determined. The WBGT index shall be measured in accordance with GBZ/T 189.7.

4.2.4 When classifying work in hot environments, the thermal insulation of the clothing worn by the workers shall be determined. The insulation coefficient of long-sleeved shirt and trousers work clothes and of textile coveralls is 0.6 Clo.

4.2.5 On the basis of the above measurement and evaluation results, classification is carried out by reference to the content of Table 1.

4.3 Classification

Work in hot environments is divided into 4 classes according to the degree of hazard, i.e. slightly hazardous work (Class I), moderately hazardous work (Class II), highly hazardous work (Class III) and extremely hazardous work (Class IV) (Table 1).