How to recognize and prevent heat stress

How to recognize and prevent heat stress
By Carola Hicks
May 31, 2011


Heat illness occurs when a combination of hot temperatures, high humidity and physical activity overcomes the body’s natural cooling system. It can cause symptoms ranging from cramps to serious heat exhaustion or even heat stroke. Employers have a legal obligation to safeguard workers from injury and illness, including the risk of heat stress.

The law

In every province, occupational health and safety legislation requires employers to keep a workplace free of recognized hazards that cause, or are likely to cause, serious physical harm or death. A hazard is considered “recognized” if the hazard is generally recognized in the employer’s industry. Canadian employers have been penalized for not protecting employees against heat-related injuries. In 2004, an Ontario bakery was fined $215,000 after an employee died of heat stroke. The temperature in the bakery was 36 C, and the outside temperature 34 C. The bakery had a heat stress plan but hadn’t implemented it at the time of the accident. Some provinces, including British Columbia and Saskatchewan, have regulations requiring specific measures be implemented to protect employees from extreme heat.

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Guidelines for implementing heat stress prevention measures include :

  • Engineering controls – ensure work areas are adequately ventilated
  • Consider physical conditions in the workplace, including ambient air temperature, radiant heat, air movement and high humidity. Those who are overweight, out of shape, over 40-years old, have pre-existing medical conditions, on medication that blocks sweating, abuse drugs or alcohol or have had heat stress before are at particular risk of heat stress.
  • Consider physiological factors. Some employees are more susceptible to heat stress. Consider all factors that can elevate the risk of heat stress, including age, weight, physical fitness level, existing medical conditions and any past heat-related injuries.
  • Educate employees about the dangers. Heat illness does not strike without warning. There are signs and symptoms associated with the various forms of heat illness, e.g. heat cramps, heat rashes, heat exhaustion or fatigue and, the most dangerous, heat stroke, collectively referred to as “heat stress.”

Recognizing heat stress

Heat cramps are painful muscle spasms caused by loss of salt from excessive sweating.

If an employee is experiencing heat cramps:

  • Get the victim to rest in a cool place.
  • Give the victim a cool drink sprinkled with salt as well as some sort of salty food. Do not give salt tablets!
  • Remove wet or tight clothing that may be restricting blood flow to the affected area.
  • If cramps continue, seek medical help.

Heat exhaustion is a more advanced and serious stage of heat stress. Symptoms of heat exhaustion include general fatigue; weakness and poor muscle control; dizziness, fainting and visual disturbances; headache and nausea; pale, cool, clammy skin or heavy sweating; cramps, and rapid pulse and breathlessness

Heat stoke is a condition in which the body’s temperature rises above 41 C and, if left untreated, can immediately result in coma, brain damage or death. Symptoms of heat stroke include hot, dry flushed skin, usually with no sweating; agitation and confusion; headache, nausea and vomiting; irregular pulse; rapid, shallow breathing; possible seizure and loss of consciousness, and possible shock and cardiac arrest.

Seek medical attention at once if an employee is experiencing heat exhaustion or stroke as both are life threatening!

While waiting for help to arrive:

  • Check the victim’s airway, breathing and circulation; give CPR, if needed.
  • Cool the victim with a sponge or spray; cover ice packs with cold wet cloths and place under armpits and groin; fan the victim
  • Move victim to cool area
  • Loosen or remove victim’s outer clothing
  • If conscious, give the victim a cool drink sprinkled with salt as well as some sort of salty food; do not give salt tablets!

Preventing heat stress

To guard against heat stress:

  • Drink about two glasses (half-litre) of water before starting work and one glass every 20 minutes while working.
  • Wear loose clothes made of cotton, silk and other fabrics that let air pass through. Wear temperature-controlled, or anti-radiant heat, or reflective clothing.
  • Allow for acclimatization when starting a new job or returning after a prolonged absence.

All persons working in hot conditions must receive adequate training and education so that they are able to recognize early warning signs and symptoms of heat-related illness, especially heat stroke. While such education isn’t just required by law, it can mean the difference between life and death. Trained employees can identify the symptoms of heat stress, both in themselves and others, and initiate the appropriate first aid measures needed to respond quickly.

About the author

Carola Hicks is CEO of Workplace Safety Group, providing leading-edge, online and in-class health and safety consultation and training programs to associations and specialty industries across Canada. Carola can be reached at

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