Heat Exhaustion
Quick answer
Heat exhaustion is what happens when the body can no longer cool itself effectively during work in hot conditions. Warning signs include heavy sweating, dizziness, headache, nausea, muscle cramps and unusual tiredness. Left unmanaged it can progress to heat stroke — a medical emergency. Every employer with heat-exposed workers should be able to recognise it and know what to do.
What heat exhaustion is
Heat exhaustion is a heat-related illness that occurs when the body loses too much water and salt through sweating and can no longer regulate its own core temperature effectively. It typically develops gradually, over minutes or hours, in workers exposed to hot or humid conditions — indoors or outdoors.
It is not the same as simply 'feeling hot'. Heat exhaustion is a physiological event: blood pressure drops, the heart works harder, judgement and coordination deteriorate, and the person becomes unable to continue working safely. Without action, it can progress to heat stroke, which is a life-threatening emergency.
Why it matters at work
Heat exhaustion rarely happens in isolation. The first person on a crew to show symptoms is usually a warning that others are also at risk — and every workplace heat incident is a signal that the day's plan (breaks, water, shade, workload) needs to change immediately.
For a small business, a single serious heat incident can mean an ambulance call, a temporary closure, an insurance claim, a regulator visit and — most importantly — lasting harm to a valued team member. Recognising heat exhaustion early is the difference between a paid rest break and an emergency.
Why small businesses should care
Small businesses often carry the highest heat risk per head. They rarely have a dedicated safety officer, they often work with tight staffing, and one person out for a week can disrupt an entire operation. The good news: the practical steps that prevent heat exhaustion are cheap, well understood and quick to put in place.
Common mistakes
Treating it as a personal weakness
Heat exhaustion is a physiological event, not a matter of willpower. Comments like 'they'll be fine' or 'they need to toughen up' delay the response that protects the worker and the business.
Assuming water alone is enough
Water helps, but rest, shade and — critically — stopping the activity are what allow the body to recover. Handing someone a bottle and asking them to carry on is not a response plan.
Missing the difference from heat stroke
Heat exhaustion can escalate to heat stroke quickly. Confusion, loss of coordination, very high skin temperature or loss of consciousness are medical emergencies — call the emergency services immediately.
Frequently asked questions
- What is the first sign of heat exhaustion?
- Heavy sweating combined with tiredness, headache, dizziness or nausea is usually the first sign. The person may look pale, be less talkative than usual, or start making small mistakes they wouldn't normally make.
- Can heat exhaustion happen indoors?
- Yes. Kitchens, laundries, warehouses, factory floors and delivery vans regularly reach conditions where heat exhaustion is a real risk — often without the visual cues (sun, sweat, exertion) that prompt action outdoors.
- Should someone go back to work after heat exhaustion?
- Not the same day. The safest default is rest, hydration and monitoring for the remainder of the shift, and a lighter workload the following day. If symptoms persisted or the person felt confused at any point, they should be assessed by a medical professional.