Don’t Let the Heat Get You Stressed!

| July 2021

With temperatures soaring, it is important to be aware of the dangers of heat stress and how to prevent them. Over-exposure to hot temperatures can cause a number of health conditions, some of which can be extremely dangerous. Heat stress occurs when the body cannot compensate for hot external conditions.

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Health conditions and their symptoms related to the heat include:

  • Heat rash: clusters of blisters; rash
  • Heat cramps: heavy sweating, muscle pains or spasms
  • Heat exhaustion: heavy sweating; cold, pale clammy skin; dizziness, headache, nausea, fainting
  • Heat stroke: fast, strong pulse; hot dry red skin; nausea, dizziness, fainting This is a medical emergency! Get medical help immediately!

Medical attention for fainting, heat exhaustion and heat stroke is crucial.


People can get used to working in the heat so they don’t react as badly to hot conditions. The acclimatization process usually takes a few weeks. When temperatures first rise during the warm weather season, people should break themselves in gradually by not working or exercising as hard until they are acclimatized.

How is the potential for heat stress assessed?

In addition to high temperatures, humidity, air movement (e.g. wind), radiant heat (e.g. direct sunlight or hot equipment), clothing, and how hard you are working or exercising also play a role in causing heat stress.

Health and safety professionals may use different kinds of indexes that combine measurement of these factors to assess the danger of heat stress. A commonly used index is called the Wet Bulb Globe Temperature (WBGT). It combines measurements for air temperature, radiant heat, and humidity. WBGT may be reported in terms of degrees Celsius or Fahrenheit.

Exposure guidelines for heat stress have been recommended by the American Conference of Governmental Industrial Hygienists (ACGIH). These guidelines are available on the Canadian Centre for Occupational Health and Safety (CCCOHS) website.

The Humidex is an easier way of assessing temperature conditions. It combines air temperature and humidity levels. Environment Canada reports the Humidex daily for your location on its website.

The following is advice from Environment Canada about Humidex levels:


Prevent Heat Stress!

If workers are required to work in hot conditions, employers should have a heat stress plan. Individuals should also be familiar with how to protect themselves from heat stress. Important elements of heat stress prevention include the following:

  1. Be aware of thermal conditions and don’t exceed recommended exertion levels or time spent in hot conditions. Take frequent breaks. When you become acclimatized to the heat, you can gradually increase your exertion levels.
  2. Check the Humidex levels so you know whether you are working in dangerous conditions.
  3. Stay hydrated by drinking plenty of fluids. But make sure you don’t drink too much. You can check the colour of your urine to make sure that you are hydrated enough. A colour chart and hydration guidelines are available here.
  4. Wear lightweight and light-coloured clothing that permits evaporation.
  5. Use sunscreen if you are out in the sun.

For more information on protecting yourself and your workers, see this guide.

Marianne Levitsky

Senior Industrial Hygiene Associate

Marianne Levitsky is a Certified Industrial Hygienist/Registered Occupational Hygienist and a Senior Industrial Hygiene Associate at ECOH, where she has been involved in developing ECOH’s COVID-19 response and advising clients on re-opening plans. She was founding President of Workplace Health Without Borders, a non-profit organization that engages volunteers in promoting occupational health for workers everywhere. She was previously Director, Best Practices, Prevention for the WSIB and an occupational hygienist with the Ontario Ministry of Labour. She is adjunct faculty at the University of Toronto and was a member of the Toronto Board of Health. Marianne has received the OHAO Hugh Nelson award and the Yant Award from AIHA, both of which recognize excellence in occupational hygiene. She has served as chair of the AIHA International Affairs Committee and is an AIHA Fellow.

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