Working in Heat

There are several factors that need to be considered when determining if there is a risk of heat illness to workers and ways to protect them.

When identifying heat hazards and controlling heat risks, workers likely to be exposed to heat as well as their health and safety representatives (HSRs), if any, must be consulted.

Air temperature alone cannot be used to determine whether there is a risk of heat illness. The key risk factors that need to be taken into account are:

• air temperature
• humidity (in the environment or workplaces such as laundries and mines)
• radiant heat (from the sun or other sources such as furnaces and ovens)
• air movement or wind speed
• workload (nature of the work and duration)
• physical fitness of the worker (including acclimatisation and any pre-existing conditions e.g., overweight, heart/ circulatory diseases, skin diseases or use of certain medicines)
• clothing (including protective clothing such as overalls, coveralls and suits worn during insecticide spraying).

If there is a risk of heat illness at work, it must be controlled. Advice may be sought from a person competent in heat assessment. They can provide recommendations about how the risk can be controlled.

Any assessment should include an appropriate heat stress index. A commonly used and recognised index is the Wet Bulb Globe Temperature (WBGT). The WBGT takes into account air temperature, radiant heat, humidity, and air movement. Adjustments are also made to take into account things such as physical workload, clothing, and work organisation.

 If a risk of heat illness is identified, control measures need to be put in place. Workers considered at risk due to factors such as pre-existing conditions should be assessed by a doctor.

The risk can also be minimised by modifying workload. This may include:

• rescheduling work so the hot tasks are performed during the cooler part of the day
• doing the work at a different location
• wearing light clothing that still provides adequate protection
• reducing the time spent doing hot tasks (e.g., job rotation)
• arranging for more workers to do the job
• providing extra rest breaks in a cool area
• using mechanical aids to reduce physical exertion

Other measures for preventing heat illness include:

• keeping people away from hot processes
• allowing workers to acclimatise
• providing cool drinking water near the work site. During hot weather, workers should be encouraged to drink a cup of water (about 200 mL) every 15 to 20 minutes, and not rely solely on soft drinks or caffeinated drinks
• providing personal protective equipment (PPE) such as reflective aprons and face shields for reducing exposure to radiant heat. Outdoor workers should be provided with protection against ultraviolet exposure, such as wide brim hat, loose fitting, long-sleeved collared (preferably cotton) shirt and long pants, sunglasses and sunscreen
• providing workers with information, instruction and training on recognising heat-related illness and on first aid. Adequate supervision of workers is also required
• providing first aid facilities and access to medical help

Use engineering controls to prevent or minimise heat illness. Examples include:

• increasing air movement using fans
• installing shade cloth to reduce radiant heat from the sun
• installing shields or barriers to reduce radiant heat from sources such as furnaces
• removing heated air or steam from hot processes using local exhaust ventilation
• installing air conditioners or coolers to reduce air temperature and generate air movement
• locating hot processes away from people
• insulating/enclosing hot processes or plant
• isolating workers from the hot process by locating them in air conditioned control rooms.

If symptoms occur, workers need to rest in a cool, well-ventilated area and drink cool fluids. If symptoms do not improve quickly, or skin is very hot and dry to touch, seek urgent medical help.

Plan ahead and ensure all necessary measures for preventing heat illness can be implemented when hot weather is predicted.