Heat Stress at Work: An Often-Overlooked Occupational Risk
As summer temperatures rise, one occupational hazard tends to get far less attention than it deserves: heat stress. It doesn’t make headlines the way falls from height or machinery incidents do, but for anyone working outdoors, in vehicles, or in poorly ventilated indoor environments, it’s a real and preventable risk — and one that employers have a legal duty to manage.
What Is Heat Stress?
Heat stress occurs when the body is unable to cool itself effectively, causing core body temperature to rise. Left unmanaged, it can progress from mild discomfort to heat exhaustion and, in severe cases, heat stroke — a medical emergency.
Early signs to watch for in yourself and colleagues include:
• Headaches and dizziness
• Excessive sweating or, conversely, a lack of sweating
• Muscle cramps
• Fatigue and irritability
• Nausea
If these symptoms progress to confusion, loss of consciousness, or a very high body temperature, this is a medical emergency requiring immediate attention.
Who’s Most at Risk?
Heat stress isn’t limited to outdoor construction workers, although they’re often the most visibly exposed group. Consider also:
• Drivers spending long periods in vehicles
• Warehouse and factory staff working near machinery or in poorly ventilated buildings
• Anyone wearing heavy PPE, which restricts the body’s ability to lose heat
• Workers with pre-existing health conditions, or those not acclimatised to hot conditions (for example, after time off or a spell of unusually hot weather)
The Legal Position
Under the Health and Safety at Work etc. Act 1974, employers have a duty to ensure, so far as is reasonably practicable, the health, safety and welfare of their employees. While the UK doesn’t currently set a specific maximum working temperature in law, this general duty still applies in hot conditions — meaning employers need to take reasonable, practical steps to manage the risk.
For construction sites, this sits alongside the wider duties under CDM 2015, and for any workplace, it feeds into the broader requirement to assess and control risks under the Management of Health and Safety at Work Regulations 1999.
Practical Steps to Manage the Risk
You don’t need an elaborate policy to make a real difference. Simple, consistent measures go a long way:
- Water access. Make sure cool drinking water is readily available, and encourage regular drinking — not just when someone feels thirsty, since thirst is already a sign of mild dehydration.
- Shade and rest breaks. Where possible, provide shaded areas for breaks and build in more frequent short breaks during the hottest parts of the day.
- Work scheduling. Consider shifting the heaviest or most physically demanding tasks to cooler periods — early morning or later in the afternoon.
- Appropriate clothing. Lightweight, breathable clothing where the task allows, and sun protection for anyone working outdoors for extended periods.
- Training and awareness. A short toolbox talk covering the signs of heat stress, and what to do if a colleague is affected, costs very little time but could prevent a serious incident.
- Monitoring vulnerable individuals. Keep an eye on anyone newly returned to site work, those with health conditions, or workers who seem to be struggling more than others.
Building This Into Your Management System
Heat stress management doesn’t need to be a standalone exercise — it fits naturally into existing risk assessment processes, particularly for outdoor or physically demanding roles. If you’re working towards ISO 45001 or reviewing your existing health and safety arrangements, seasonal risks like this are a good example of the kind of hazard that should be captured, reviewed, and revisited as conditions change throughout the year.
If you’d like support reviewing your site or workplace arrangements for hot weather, building heat stress into your risk assessments, or strengthening your wider health and safety management system, PMBSafety can help.
Contact: paul@pmbsafety.co.uk