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Heat stress

Our bodies naturally maintain a temperature between 36°C and 38°C. Sweating cools our bodies down, but if you work in a hot environment this might not be enough. If your body heats up faster than it can cool itself, you experience heat stress. This can lead to serious heat disorders and potential injury.

How workers are exposed

There are three main causes of heat stress. They are:

The environment
  • Radiant heat from direct or indirect sunlight (reflection from pavement or kilns)
  • Air temperature hotter than skin temperature (warms a worker up)
  • High humidity (makes it harder for a worker to cool down)
The work
  • The more active you are, the more heat you will produce
The worker
  • Conditioning (regular work in hot environments makes workers less prone to heat stress)
  • Poor health, including obesity, advanced age, and medical conditions (the body responds poorly to overheating)
  • Not staying hydrated
  • Excess clothing or inappropriate personal protective equipment (they trap heat and prevent cooling)

The dangers to workers

As a worker's body heats up it loses fluids and salt through sweat. As workers dehydrate they are less able to cool themselves down. Workers in a hot environment should be aware of these warning signs of heat stress:

  • Excessive sweating
  • Dizziness
  • Nausea

If heat stress is not recognized and treated early, it can lead to heat disorders, which have serious effects on the body. These include:

Heat cramps
  • Painful muscle cramps
  • Can lead to heat exhaustion if left untreated
Heat exhaustion
  • Shallow breathing
  • Increased heart rate
  • Weak, rapid pulse
  • Cool, pale, clammy skin
  • Sweating
  • Weakness, fatigue, dizziness
  • Headache and nausea
  • Fainting
  • Muscle cramps
  • Can lead to heat stroke if left untreated
Heat stroke
  • Hot, dry, flushed skin
  • No longer sweating
  • Agitation and confusion
  • Decreased level of consciousness and awareness
  • Headache
  • Nausea and vomiting
  • Seizures
  • Increase in breathing rate
  • Irregular pulse
  • Shock
  • Cardiac arrest

How to protect workers

The most effective way to reduce the risk of heat stress is to eliminate the source of exposure. If that's not possible, there are other risk controls to use. When choosing risk controls, start by asking yourself the questions in the following steps, which are listed in order of effectiveness.

  1. 1

    Elimination or substitution

    Eliminating the hazard by substituting a safer process or material, where possible, is the most effective control. A question to consider:

    • Can the job be done in a cooler environment?
  2. 2

    Engineering controls

    Making physical modifications to facilities, equipment and processes can reduce exposure. Some questions to consider:

    • Can ventilation be improved?
    • Can hot surfaces be insulated or covered to reduce radiant heat?
    • Can shields and barriers be installed to protect workers from heat?
    • Can humidity be reduced?

  3. 3

    Administrative controls

    Changing work practices and work policies, awareness tools, and training can limit the risk of heat stress. Some questions to consider:

    • Can warning signs be posted in the work area?
    • Can cool-down rooms be provided?
    • Can workers be acclimated to heat?
    • Can water be provided?
  4. 4

    Personal protective equipment

    This is the least effective control. It must always be used in addition to at least one other control. Some questions to consider:

    • Do workers have heat-reflective clothing or water-cooled suits?
    • Has personal protective equipment been tested to make sure it is working properly?