OCC/Physical Health/TBT-OCC-010

Heat Exhaustion and Heat Stroke

Occupational Health › Physical Health › Heat Exhaustion and Heat Stroke

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Heat exhaustion occurs when the body overheats and cannot cool itself through sweating effectively.
Heat stroke is a medical emergency where core body temperature exceeds 40°C and organs begin to fail.
Construction workers performing heavy physical tasks in hot weather are at high risk of heat illness.
Symptoms of heat exhaustion include heavy sweating, weakness, dizziness, nausea, and headache.
Heat stroke symptoms include confusion, hot dry skin, loss of consciousness, and seizures.
Dehydration accelerates heat illness; workers should drink water regularly before feeling thirsty.
Dark-coloured clothing, heavy PPE, and working in direct sunlight all increase heat buildup.
Acclimatisation takes 7 to 14 days; new workers and those returning from leave are more vulnerable.
Heat illness can develop quickly in UK summer conditions, especially during heat wave events.
Employers must assess heat risk under MHSWR 1999 and provide adequate controls and welfare.

Prevent death	Heat stroke is fatal without immediate treatment. Core temperature above 40°C causes brain damage, organ failure, and death.
Common risk	UK summers increasingly produce heat wave conditions. Outdoor construction workers are among the most exposed occupational groups.
Rapid onset	Heat illness progresses from mild exhaustion to life-threatening stroke within minutes if warning signs are ignored.

Don't

Drink water frequently throughout the day, before you feel thirsty.
Take rest breaks in shade at regular intervals during hot weather.
Schedule heavy physical tasks for cooler morning and evening hours.
Watch colleagues for signs of heat exhaustion including confusion and dizziness.
Move anyone showing heat stroke symptoms to shade and cool them immediately.
Call 999 for heat stroke; it is a life-threatening medical emergency.
Allow new workers 7 to 14 days to acclimatise to hot working conditions.
Provide shade, cold water, and cooling facilities at the work location.
Wear lightweight, light-coloured clothing where PPE requirements allow.
Monitor weather forecasts and implement heat action plans when temperatures rise.

DON'T wait until you feel thirsty to drink water; by then you are already dehydrated.
DON'T ignore dizziness, nausea, or heavy sweating; these are heat exhaustion warnings.
DON'T schedule heavy physical work during the hottest hours of the day.
DON'T leave a worker with heat stroke symptoms unattended; stay until help arrives.
DON'T rely on caffeinated drinks or energy drinks as your main fluid intake.
DON'T dismiss confusion or disorientation in hot weather as tiredness.
DON'T remove PPE in hazardous areas to cool down; find an alternative solution.
DON'T expect new workers to work at full pace in heat before acclimatising.
DON'T assume UK summers are too mild for heat illness; heat waves are increasing.
DON'T delay calling 999 if someone collapses with hot dry skin and confusion.

See also: Summer Heat and Hydration | Welfare in Extreme Weather

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