Working safely in hot conditions

The key risk factors to consider are:

• air temperature
• humidity (high humidity limits the evaporation of sweat which is 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 – the intensity and duration of the work
• physical fitness of the worker including acclimatisation and any pre-existing conditions such as obesity, heart/circulatory diseases, skin diseases or use of certain medicines that affect the body’s ability to manage heat (e.g. diuretics, antidepressants and anticholinergics
• clothing (including protective clothing that may restrict air flow across the skin and hinder evaporation of sweat).

The risk assessment should be carried out by a person competent in heat assessment and may include 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 and adjustments such as physical workload, clothing and the 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, PCBUs need to put control measures in place. Workers considered more at risk due to factors such as pre-existing medical conditions should be medically assessed.

Where the employer has implemented practical controls, but is unsure as to whether there is a still a health risk, various forms of risk assessment tools can be utilised:

• Heat Stress basic calculator that does not need WBGT (Worksafe Queensland)
• 2024 TLVs and BEIs (ACGIH)
• Heat Stress Checklist - Risk Assessment Work Sheet (Health and Safety Executive UK)

Some of these assessments require information such as the WBGT.

This should preferably be measured in the work area, however as a guide, the Bureau of Meteorology provides WBGT values for major centres and occupational hygienist can also assist with such assessments.

In some cases, such as when full impermeable suits are worn, direct physiological monitoring of each worker may be required to monitor heat stress.

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 cloth 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
• installing air conditioners or coolers to reduce air temperature
• locating hot processes away from people and
• insulating /enclosing hot processes or plant.

Reducing heat stress requires careful work organisation, such as:

• rescheduling work so that hot tasks are performed during the cooler part of the day or in the cooler times of the year
• reducing the time an individual spends doing the hot tasks, e.g. by job or task rotation
• arranging for more workers to do the job
• providing additional rest breaks in cool, shaded areas and
• using mechanical aids to reduce physical exertion.

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 and pre-start meetings are key to reinforcing actions that prevent heat illness.

Providing PPE such as reflective aprons and face shields can reduce exposure to radiant heat. Ice vests and liquid and air circulating systems can be worn under PPE where appropriate.

Outdoor workers should be provided with protection against ultraviolet exposure such as a wide brim hat, loose fitting, long sleeved collared shirt and long pants, sunglasses and sunscreen.

There are many ways heat illness can be prevented in your workplace:

• replace lost fluids - encourage drinking 250 ml of water every 15 to 20 minutes during hot work conditions. Regulation r. 41A of the Work Health and Safety (General) Regulations 2022 requires that a supply of clean, cool drinking water is provided and readily accessible to workers. Workers should be encouraged to start their shift fully hydrated. Keeping well hydrated is a critical factor in avoiding heat illness which should be reiterated to your workers during workplace inductions.
• limit caffeine, carbonated drinks, alcohol and tobacco use
• have rest breaks in a cool place
• do not take salt tablets unless specifically advised by your doctor
• inform your PCBU if you have an underlying health condition that may increase your risk of heat illness
• maintain a healthy diet with regular exercise
• wear cool clothing, a wide brimmed hat and use sunscreen
• take a break and tell your manager if you are feeling tired, dizzy or weak or having trouble concentrating.

Although water is generally adequate for fluid replacement, low joule cordials and electrolyte replacement solutions may be provided to encourage fluid intake. High sugar cordials and sports drinks are not recommended.

Workers, in particular those with fly-in fly-out (FIFO) contracts may experience significant differences in climatic conditions between the workplace and their off-work location, especially after an extended absence.

Suitable acclimatisation procedures should be considered for workers who are subject to hot work conditions. These procedures should be developed in consultation with workers and consider the particular shift roster schedules used.

Other controls to eliminate or reduce heat stress include providing:

• adequate supervision of workers
• first aid facilities, instruction and training and access to medical help.

Employers should plan ahead and ensure that all the necessary measures for preventing heat illness can be implemented when hot weather is predicted.