Heat and outdoor work risk assessment

Scope note

There is no single temperature at which work must stop. Risk depends on air temperature, humidity, radiant heat, air movement, workload, clothing and the individual, and a moderate temperature with high humidity and heavy work in protective clothing can be more dangerous than a hotter dry day at rest. Where your jurisdiction, industry standard or agreement sets specific thresholds or measures, record them below rather than relying on a remembered number.

Assessment details

Step 1 - Environmental conditions

• Air temperature expected during the work period
• Humidity, which limits the body's ability to cool by sweating
• Radiant heat: direct sun, hot surfaces, plant, furnaces or reflective ground
• Air movement: still air in trenches, tanks, roof spaces and enclosed areas
• Shade availability at the work location, not just at the compound
• Forecast checked for the work period, including consecutive hot days
• Overnight temperatures considered, since poor recovery sleep compounds the risk

Step 2 - The work and the clothing

• Workload intensity: light, moderate, heavy or very heavy
• Duration of continuous exertion, and the pace set by the schedule
• Protective clothing and PPE that limit heat loss, including coveralls and respirators
• Manual handling or repetitive exertion adding metabolic heat
• Confined or enclosed spaces where heat accumulates
• Whether the task can be rescheduled to a cooler part of the day
• Whether the task can be mechanised or the exertion reduced

Step 3 - The people

• New or returning workers identified as unacclimatised, and given a graduated start
• Acclimatisation plan in place, recognising it is lost after time away
• Age, fitness, body composition and pregnancy considered
• Medical conditions and medications that affect heat tolerance considered confidentially
• Recent illness, particularly with fever, vomiting or diarrhoea
• Alcohol or caffeine intake and sleep quality discussed as part of fitness for work
• Prior history of heat illness, which increases susceptibility
• Workers know they must report symptoms in themselves and others without penalty

Step 4 - Controls

• Reschedule heavy work to the coolest part of the day, or to another day
• Provide shade at the work location, including portable shade
• Mechanical ventilation, fans or cooling in enclosed hot areas
• Cool drinking water within easy reach of the work, not a walk away
• Structured work and rest cycles that shorten as conditions worsen
• Rest area that is genuinely cool, with seating and water
• Buddy system so workers watch each other for symptoms
• Lighter or ventilated PPE where it provides equivalent protection
• Supervisor monitoring of conditions through the shift, not just at start
• Clear stop-work trigger, agreed in advance and honoured without argument

Step 5 - Recognising and responding to heat illness

Everyone on site should be able to recognise these. Heat stroke is a medical emergency and the person may not recognise it in themselves, which is why the buddy system matters.

• Early signs: heavy sweating, thirst, fatigue, muscle cramps, headache
• Heat exhaustion: dizziness, nausea, weakness, clammy skin, rapid pulse, fainting
• Heat stroke: confusion, slurred speech, agitation, loss of consciousness, seizures, skin that may be hot and dry or still sweating
• Any confusion or altered behaviour in the heat is treated as heat stroke until proven otherwise
• First response: stop work, move to shade or a cool area, remove excess clothing, begin active cooling, give fluids only if fully conscious
• Call 111 immediately for suspected heat stroke, and keep cooling while waiting
• Never leave an affected worker alone, and never send them home to recover unsupervised
• All heat illness is reported and investigated, including cases that resolved with rest

Risk table