Occupational Hygiene

Thermal comfort in the Environment

Thermal comfort in the Environment

Thermal Comfort is that condition of mind which expresses satisfaction with the thermal environment.  In terms of bodily sensations, thermal comfort is a sensation of hot, warm, slightly warmer, neutral, slightly cooler, cool and cold.

Six factors affecting thermal comfort are both environmental and personal.  These factors shown below may be independent of each other, but together contribute to a workers thermal comfort.

Thermal comfort

Environmental factors:

  • Air temperature
  • Radiant temperature
  • Air velocity
  • Humidity

Personal factors:

  • Clothing insulation
  • Metabolic heat

Measuring the thermal environment is protecting the health of the workers operating in hot or cold environments and ensuring thermal comfort in indoor environments.

The risk to health associated with thermal stress, stems from poor well-being, inadequate work capacity or heat intolerance.

The assessment of the thermal environment must satisfy three objectives, namely:

  • Ensure that a safe thermal environment prevails on a day-to-day basis;
  • Provide meaningful input to the process of general risk management and review; and
  • Avoid thermal discomfort in indoor environments.

Temperature can influence our life-style, clothing and fashion, conversations and even our moods.  “Temperature” or, more appropriately, the thermal environment, also has a Thermal comfort - 2



major impact on health, safety, productivity and comfort.






The comfort limit is a zone of ambient temperatures where a person can work free from temperature stress.  A characteristic of the zone is that the worker does not need to wear excessive or protective clothing.


Temperatures ranging between the limits of 16 – 24°C appear to be acceptable.  Individuals who do heavy work (high oxygen consumption) prefer working in the “cold limit” (i.e. closer to 16°C), while individuals performing light work (low oxygen consumption) prefer working in the “warm limit” (i.e. closer to 24°C).  Individual preferences also play a role because individuals experience heat and cold differently.

If ambient conditions exceed a temperature of 28°C wet-bulb and/or 35°C dry-bulb, a more detailed evaluation must be carried out.


  1. Occupational Hygiene – Johannes J. Schoeman, Herald H.E. Schröder 1994, Juta & Co, LTD.
  2. MHSC – Handbook on Mine Occupational Hygiene Measurements : D.W. Stanton, J. Kielblock, J.J. Schoeman, J.R. Johnston – Mine Health and Safety Council JHB 2007

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