Working safely in hot conditions - Heat stress

Heat stress may affect people in all parts of Western Australia during our summer months and may affect workers at some workplaces throughout the year. The effects of heat stress range from discomfort to life threatening illnesses such as heat stroke.  Bulletin   Poster

What is heat stress?

Heat stress is the total heat burden to which the body is subjected by both external and internal factors.

The body must balance the heat transferred into the body, heat generated in the body and heat coming out of the body.

What are the effects of heat stress?

If the body can’t balance heat inputs, heat stress may lead to heat illness (or heat strain), a physical response designed to reduce body temperature.

Types of heat illness include:

  • discomfort - flushed skin, increased sweating, heat rashes (prickly heat); 
  • mild heat illness - feeling tired, weak or dizzy, cramps, reduced work capacity, reduced attention span, irritability; 
  • heat exhaustion - fainting, headache, low blood pressure, nausea, clammy, pale or flushed skin, normal to high body temperature (up to 39C);
  • heat stroke - irritability, confusion, speech problems, hot dry skin, convulsions, unconsciousness, body temperature above 40C, cardiac arrest - potentially fatal.

Heat stress causes increased blood flow to the skin, which allows release of heat. Blood is diverted to the muscles if physical work is being performed, resulting in a lower release of heat through the skin.

Are some people more prone to heat illness?

People who are medically unfit, are on certain medications, overweight, have heart disease, are pregnant, abuse alcohol, or are not acclimatized, are at a greater risk of heat illness and should heed medical advice. Some people are less tolerant of heat than others.

Acclimatisation takes 7-14 days to take effect, and can be reduced after three days away from hot work. Acclimatisation is entirely lost after four weeks away from hot work. 

Reducing the risk of heat illness 

Under the Occupational Safety and Health Act 1984 employers are required to provide a working environment in which workers are not exposed to hazards.  Workers are required to take reasonable care to ensure their own safety and health and that of others at work. 

The Occupational Safety and Health Regulations 1996, (Regulation 3.15) require employers protect workers from extremes of heat and also requires air cooling be provided in indoor workplaces (where practical) for comfort reasons.

There is a recommended order of control measures that eliminate or reduce the risks of injury or harm. Often a combination of controls will be necessary. 


Engineering controls are an effective way of reducing heat stress and preventing or minimising occurrence of heat illness.

Examples include: 

  • increasing air movement using fans;
  • installing shade structures to reduce radiant heat from the sun;
  • installing shields or barriers to reduce radiant heat from sources such as furnaces or hot vessels;
  • removing heated air or steam from hot processes using local exhaust ventilation;
  • insulating indoor workplaces;
  • installing air conditioners or coolers to reduce air temperature;
  • locating hot processes away from people; 
  • insulating /enclosing hot processes or plant; and
  • using mechanical aids to reduce physical exertion.

Organisation of work

Heat stress can be reduced by attention to the way work is organised. 

Examples include:

  • rescheduling work so the hot tasks are performed during the cooler part of the day or in cooler times of the year; 
  • reducing the time an individual spends doing the hot tasks eg. by job or task rotation; 
  • arranging for more workers to do the job; 
  • making sure there is easy access to cool drinking water; and
  • providing additional rest breaks in cool, shaded areas. 

Personal protective equipment

Personal protective equipment may be needed to further reduce the risk of heat illness. This may include: 

  • broad brimmed hat
  • appropriate protective clothing (outdoor workers should ensure clothing covers them at least between elbow and knee, however long sleeves and pants provide the best protection). 
  • sunscreen
  • sunglasses

Providing training and information

Training and information will enable workers to:

  • identify hazards associated with heat stress;
  • recognise symptoms of heat stress and heat illness;
  • identify appropriate first aid procedures;
  • understand how to avoid heat illness;
  • recognise the potential dangers associated with the use of alcohol and/or drugs; and 
  • use appropriate protective clothing and equipment.

Toolbox meetings and pre-start meetings present opportunities to reinforce the actions needed to avoid heat illness.

Risk assessment 

Where the employer has implemented practical controls, but is not sure whether there is a still a health risk, various forms of risk assessment are available, for example: 

Some of these assessments require information such as the Wet Bulb Globe Temperature (WBGT). 

This should preferably be measured in the work area, however as a guide, the Bureau of Meteorology provides WBGT values for major centres. An occupational hygienist can assist with such assessments. In some cases (eg when full impermeable suits are worn), direct physiological monitoring of each worker may be required to monitor heat stress.

Tips for avoiding heat illness

  • Replace lost fluids (drink more water, juice, sports drinks or other non-alcoholic drinks). Drinks of 100-200ml water at frequent intervals will be adequate to reduce fluid loss in sweating; 
  • Have rest breaks in a cool place; 
  • Minimise caffeine, carbonated drinks, alcohol and tobacco use; 
  • Do not take salt tablets unless your doctor has specifically advised you to do so; 
  • Inform your employer if you have an underlying health condition that may increase your risk of heat illness; 
  • Maintain a healthy lifestyle (healthy diet and regular exercise); 
  • Wear cool clothing, a wide brimmed hat and use sunscreen; and 
  • Take a break and tell your boss if feeling tired, dizzy or weak or you're having trouble concentrating.

Make the job safe - talk about safety and heath at work

If you believe there are problems with heat stress at your workplace you should discuss them with your employer and your safety and health representative.

How should heat illness be treated?

Have the person rest in the coolest available place and drink cool but not cold fluids. Provide an electrolyte supplement or sports drink if available.

Contact a doctor, nurse, ambulance service or first aid officer if the symptoms do not reduce quickly or if symptoms of heat stroke are present.

References and further information 

For more information on working safely in the sun 

Related information

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