• What law applies
• Working in the sun and heat
  • The risks of working in the sun
  • Workers most at risk
• The sun and its health effects
• Sun safety measures
  • Sun exposure in Queensland
  • Controlling sun exposure
  • Personal protection
  • Sunscreen
  • Training
• Heat stress
  • Causes and sources of heat stress
  • Heat related illness
  • Hydration
• Artificial sources of ultra violet radiation

• Personal protective equipment
• Risk management

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Causes and sources of heat stress

Understanding heat stress
Environmental factors
Controlling exposure

Understanding heat stress

Heat stress occurs when heat is absorbed from the environment faster than the body can get rid of it. Several factors may contribute to heat stress, such as the:

• type of work activity
• surrounding air temperature/humidity level
• physical condition of the individual (he/she may be new to the job or new to Queensland).

Our bodies maintain a fairly constant internal temperature even though they may be exposed to varying environmental temperatures.

To keep internal body temperatures within safe limits in hot conditions, the body has to get rid of excess heat - and it does this by evaporating sweat and varying the blood flow to the skin. These responses are controlled by the brain and usually occur when the blood exceeds 37 degrees centigrade.

Factors that may contribute to heat-related health problems at work include:

• inadequate cooling off or rest periods
• insufficient water consumption
• climatic conditions (such as low air movement, high humidity levels and high air temperature)
• inappropriate clothing
• individual factors that may cause dehydration (such as poor diet, vomiting, diarrhoea or alcohol and caffeine consumption)
• individual medical conditions that may cause heat stress (such as heart problems, diabetes or hypertension)
• individual medication that may affect the body's temperature regulation
• an individual's age, general physical fitness and weight.

Environmental factors

Environment and seasonal factors that can contribute to heat problems include:

• high air temperatures
• higher relative humidity levels
• low air movement
• radiant heat from plant (dryer, oven, furnace) or processes such as smelting, molten metals
• radiant heat from working outdoors in the sun.

Controlling exposure

Control the temperature using engineering solutions which include:

• reducing radiant heat emissions from hot surfaces and plant e.g. by insulation and shielding
• using ventilation and air-conditioning
• humidity reducing methods e.g. install a dehumidifier (seek engineering advice)
• using automation and mechanisation of physically demanding tasks to reduce the work rate.

Reduce the length of exposure by:

• using trees, buildings and other temporary shelter (tarp, umbrella) to provide workers with shade
• provide shade for rest and meal breaks.

Gradually adjust your workload when starting or returning to work in hot conditions. Generally, the process takes about a week.

Ensure workers:

• wear specialised liquid or air cooled clothing when working in extreme conditions
• are screened for heat tolerance
• follow their doctor's advice before working in hot conditions
• have a plan in place for treating heat affected workers
• drink cool water at frequent intervals to prevent dehydration
• wear loose fitting clothing to promote good air circulation.