Working safely in hot conditions Part 1

WorkSafe WA recently issued a bulletin to provide workers in that state with practical advice for employers and workers on heat illness, related health and safety problems and actions and measures to take to prevent or minimise the likelihood of heat illness. With summer coming on soon, the guidelines are relevant for Australians working outdoors.

In Australia, hot workplaces are common. Heat may come from:

• hot climatic conditions;
• heavy work in moderately hot conditions;
• hot work processes (such as welding);
• radiant heat from the surroundings;
• work where heavy protective clothing must be worn; or
• any combination of these factors.

The Occupational Safety and Health Act 1984 requires employers to provide and maintain, so far as is reasonably practicable, a working environment in which workers are not exposed to hazards. This applies to any risk to safety and health, including illness from working in heat.

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.

Heat illness occurs when the body cannot dispense the heat burden sufficiently for normal functioning to be maintained.

Heat illness

Heat illness covers a range of medical conditions which include:

• heat stroke - a life-threatening condition that requires immediate first aid and medical attention;
• fainting;
• heat exhaustion;
• heat cramps;
• rashes (also called ‘prickly heat’); and
• heat fatigue.

Signs of heat illness include feeling sick, nauseous, dizzy or weak. Clumsiness, collapse and convulsions can also be the result of heat illness and workers with these signs need to seek immediate medical attention. Working in hot conditions may aggravate pre-existing illnesses and conditions.

Managing the risk of heat illness

In identifying, assessing and controlling risks associated with heat illness, employers should consult with workers likely to be exposed to heat as well as with any elected health and safety representatives.

Identifying risk factors

The key risk factors to take into account are:

• air temperature;
• humidity (high humidity limits the evaporation of sweat - a key cooling mechanism for the body);
• radiant heat (from the sun or other sources such as furnaces, ovens and hot vessels);
• air movement or wind speed;
• workload (intensity and duration of work);
• physical fitness of worker, including acclimatisation and any pre-existing conditions such as obesity, heart/circulatory diseases, skin diseases or use of certain medicines that can affect the body’s ability to manage heat (eg, diuretics, antidepressants and anticholinergics); and
• clothing (including protective clothing that may restrict airflow across skin and hinder evaporation of sweat).

Assessing the risk of heat illness

This should be carried out by a person competent in heat assessment. The risk assessment may include the use of an appropriate heat-stress index. A commonly used and recognised index is the wet bulb globe temperature (WBGT), which takes into account air temperature, radiant heat, humidity and air movement. Adjustments can take into account such things as physical workload, clothing and work organisation.

The thermal work limit (TWL) is an alternative approach being used increasingly in Australian workplaces, particularly in the resource industry. It accounts for all of the major factors mentioned above and provides guidance on managing workloads and fluid intake. If the assessment indicates a risk of heat illness occurring, employers need to put control measures in place. Workers considered at risk due to factors such as pre-existing medical conditions should be medically assessed.

Part 2 of this article will present guidance from WorkSafe WA on reducing the risk of heat stress and preventing heat illness.