Heat Stress Action Plan

A heat stress action plan sets out the triggers and responses for managing extreme heat on construction sites.
Heat stress occurs when the body cannot cool itself sufficiently, leading to heat exhaustion and heat stroke.
UK heatwaves are becoming more frequent and intense, with construction workers among the most exposed groups.
Trigger temperatures should be defined — typically 25°C ambient temperature initiates additional controls.
The plan should include rest schedules, hydration targets, shade provision, and work rescheduling options.
Workers in direct sunlight wearing PPE can experience effective temperatures 10–15°C higher than ambient.
Acclimatisation takes 7–14 days — new workers and those returning from leave are at higher risk.
Heat stroke is a medical emergency — core body temperature exceeds 40°C with confusion and collapse.
Supervisors must be trained to recognise heat illness symptoms and take immediate action.
The MHSWR 1999 requires employers to assess and manage temperature-related risks in the workplace.

Prevent fatalities	Heat stroke is a medical emergency that can be fatal if not recognised and treated within minutes.
Worker performance	Heat stress reduces concentration, coordination, and decision-making — increasing the risk of accidents.
Employer duty	MHSWR 1999 requires assessment and control of heat-related risks for outdoor construction workers.

Do

Don't

Establish temperature triggers that activate additional heat stress controls on site
Provide free cold drinking water at multiple accessible locations around the site
Schedule the heaviest physical work for cooler parts of the day where possible
Provide shaded rest areas where workers can cool down during breaks
Increase the frequency and duration of rest breaks as temperatures rise
Train supervisors to recognise heat exhaustion and heat stroke symptoms
Allow new workers 7–14 days to acclimatise before full physical workloads
Monitor workers for signs of heat illness including confusion and excessive sweating
Apply sunscreen and wear lightweight breathable clothing under PPE where permitted
Call emergency services immediately for any worker showing heat stroke symptoms

DON'T wait for workers to collapse before activating the heat stress plan
DON'T rely on workers self-managing hydration — provide water and enforce breaks
DON'T schedule heavy manual tasks during the hottest afternoon hours in summer
DON'T ignore early symptoms of heat exhaustion such as headache and nausea
DON'T assume fit workers are immune — heat stroke can affect anyone
DON'T restrict water intake or skip rest breaks to meet production targets
DON'T give a heat stroke casualty cold water to drink if they are confused
DON'T allow new or returning workers to work at full pace without acclimatisation
DON'T dismiss heat stress as minor discomfort — it can escalate rapidly to emergency
DON'T remove the action plan triggers because the forecast looks mild for tomorrow

See also: Summer Heat and Hydration | Heat Exhaustion and Heat Stroke

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