What is heat stress?
Heat stress is a combination of factors that lead to increased heat storage in the body. It happens when the body’s thermoregulation control systems start to fail. The main way our body cools its internal temperature is by sweating, so it isn’t just hot temperatures you need to be wary of. High temperatures, high humidity and high work rate can all cause heat stress.
Know the symptoms
Heat stress, if ignored, leads to heat exhaustion, which can soon turn into heat stroke. Heat stroke is a serious heat-related illness and can be fatal if appropriate action isn’t taken quickly.
– An inability to concentrate
– Muscle cramps
– Heat rash
– Severe thirst
– Cold, clammy skin
– Hot, dry skin
– Loss of consciousness
Heat Stress Index
The higher the heat and humidity, the higher the risk level. Ensure you’re checking in with your workers regularly to determine their exposure.
46°C and above
Very high risk level
Control approach: Enhanced controls as planned with enhanced awareness control
40 to 45°C
High risk level
Control approach: Additional controls as planned with more awareness
35 to 39°C
Moderate risk level
Control approach: Implement planned controls and create awareness
Up to 34°C
Low risk level (caution)
Control approach: Basic heat safety and planning
“consider the use of cooling vests or look for specialised materials that are both breathable and safe for the work at hand”
Identify and reduce the risks
The UK’s Health & Safety Executive (HSE) has established a set of questions to ask yourself and your workers to help determine the risk of heat stress.
The HSE’s Heat Stress Checklist1:
- Does the air feel warm or hot?
- Are there any radiant heat sources? Examples include the sun, furnaces/ovens, hot surfaces and machinery, chemical reactions, molten metals, etc.
- Is there any equipment that produces steam?
- Is the workplace affected by external weather conditions?
- Are workers wearing non-permeable PPE?
- Do workers sense the air is humid?
- Is warm/hot air blowing onto workers?
- Is the work-rate moderate to intensive?
- Is PPE being worn to protect against harmful chemicals, asbestos, flames, extreme heat, etc.?
- Is respiratory protection being worn?
- Do your employees think that heat stress is a problem? •Do your employees complain of feeling warm or hot?
Limit work, increase rest
You should limit worker’s exposure to direct sun as much as possible. Avoid working at peak times of day. Evaluate the risks regularly throughout the day and consider increasing rest periods as temperature and humidity rises, where there is no air movement, when PPE is to be worn, or when performing heavier work.
Communicate any changes
Heat risk levels can be measured by different means*, and particularly weather conditions are subject to sudden or gradual changes. If humidity or temperatures start to rise above their previously assessed risk levels, then this must be communicated to workers, either by radio/mobile communications or flag signals, so that they are aware of new risks present and change their actions accordingly.
* Please refer to the heat index for more information on risk levels.
H2O on the go
Dehydration, especially in hot environments, can slow your worker’s ability to function safely at best and lead to heat exhaustion or heat stroke at worst. Deploying water stations is a great way to give workers regular access to water. Your workers need to replenish the sweat they are losing, so they must also be able to replenish lost salts. It’s recommended that a worker has a glass of water every hour and a salt/electrolyte replenishment solution every third drink.
Be picky with PPE
Heat stress risks cannot always be avoided with certain PPE needs. Consider the use of cooling vests or look for specialised materials that are both breathable and safe for the work at hand. Where heavy PPE or RPE is absolutely necessary, special work systems should be implemented, such as longer and more frequent rests, to manage symptoms.
Teach don’t preach
Training is a vital part of ensuring worker compliance, especially with
new and inexperienced workers. Workers must understand the dangers
of the work they are undertaking, and knowing the signs of heat stress and how to treat them is vital to ensure action is taken quickly before further risk to health.
Be prepared for emergencies
Have emergency procedures in place in case the worst were to happen. Ensure you have an appropriate number of first-aid trained personnel on site, you’ll have to check with your local authority for what this number may be. Ensure your workers know what phone number to call in an emergency, this varies from country to country.
Identify vulnerable workers
New workers will need to acclimate to the hot environment before more strenuous work is assigned. You should also be aware of any workers with medical conditions or health concerns. The status of an individual’s health can make them more susceptible to heat stress and so it should be monitored or screened regularly by a medical or occupational health professional.