Last edited 19 Jul 2016

Heat stress

Temperatures in the workplace are governed by the Workplace (Health, Safety and Welfare) Regulations 1992, which oblige employers to provide a reasonable temperature in the workplace.

The Approved Code of Practice (Workplace health, safety and welfare. Workplace (Health, Safety and Welfare) Regulations 1992. Approved Code of Practice ) suggests a minimum temperature of 16 °C, or 13°C if work involves severe physical effort. However, these are only guidelines, and the complexity of temperatures means there is no maximum guideline temperature.

The Health and Safety Executive (HSE) did previously define thermal comfort in the workplace, as '…roughly between 13°C and 30°C, with acceptable temperatures for more strenuous work activities concentrated towards the bottom end of the range, and more sedentary activities towards the higher end.' However, thermal comfort, particularly at higher temperatures cannot sensibly be reduced to a single measure. It is dependent on a range of environmental factors in addition to air temperature, such as; air velocity, radiant temperature, relative humidity and the uniformity of conditions. It also depends on personal factors such as; clothing, metabolic heat, state of health, acclimatisation, expectations, and even access to food and drink. See thermal comfort for more information.

Heat stress is a form of overheating that the occupants of a building may experience when the measures their body uses to regulate internal temperature begin to fail. This can occur for example in buildings where an industrial process is being carried out, such as; smelting, brick-firing, cooking and so on.

Heat stress is a personal condition; some occupants may experience heat stress whilst others may not. Where humidity is high, or occupants are wearing protective clothing that cannot be adjusted or removed, the body may be unable to lose heat through the evaporation of sweat and so individuals may begin to experience elevated deep-body temperature, excessive sweating and increased heart rate.

This in turn can lead to:

  • Dehydration.
  • Headache, difficulty concentrating and confusion.
  • Muscle cramp.
  • Heat rash.
  • Fatigue.
  • Giddiness and fainting.
  • Nausea.
  • Convulsions.

Ultimately, if it is allowed to persist, heat stress can cause death.

The Workplace Regulations, the Management of Health and Safety at Work Regulations 1999 require that employers assess the risks to the health and safety of their workers, and take action where necessary and reasonably practicable. Measures taken to reduce the risk of heat stress might include:

  • Changes to the environment or to processes to reduce activity or exposure to heat.
  • Reducing the length of exposure and allowing acclimatisation.
  • Giving access to water.
  • Using specialist personal protective equipment.
  • Training.
  • Assessing and monitoring health.

The Health and Safety Executive suggest that wet bulb globe temperature can be used as a measure of likely heat stress. It includes components of natural wet-bulb temperature (tnw), globe temperature (tg) and air temperature (ta). See wet bulb globe temperature for more information.

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