Phoenix Journal · Extraction
Heat stress builds quietly in a hot kitchen, dulling the mind and straining the body long before anyone calls it an emergency. Here is what the heat actually does to you, and how to stay ahead of it.
Health & safety
A commercial kitchen is one of the hottest indoor workplaces in the country, and the human body pays for every degree it has to fight against.
Heat stress is not simply feeling warm. It is what happens when the heat load on your body starts to outpace your ability to shed it, and the internal balance that keeps you sharp, steady and safe begins to slip. On a busy service, that slip can arrive quietly - a missed order, a slower reach for a hot pan, a moment of dizziness by the fryer - long before anyone thinks the word emergency. Understanding what heat does to the body helps you spot trouble early and design the space, and the shift, to keep it at bay.
Your body runs best at a core temperature of around 37°C and works hard to hold it there. In a hot kitchen, that defence system is under constant load, and the effects stack up through the shift.
The Health and Safety Executive frames workplace heat around six basic factors of thermal comfort, and a commercial kitchen manages to stack almost all of them against you at once. Four are environmental: air temperature, radiant temperature from ovens and hot surfaces, air velocity, and humidity. Two are personal: the clothing you wear and your metabolic rate - the heat your own body makes as you work. A chef on service is generating heat through hard physical effort, standing beside radiant surfaces, breathing humid air thick with steam, and wearing clothing that seals much of that heat in. Every one of those levers is pushed the wrong way.
Humidity deserves special attention because it is the quiet villain. Sweating only cools you when the sweat evaporates. In damp, steamy air the sweat has nowhere to go, so it drips off rather than carrying heat away, and your core temperature keeps climbing while you lose fluid for no cooling benefit. This is why two kitchens at the same air temperature can feel worlds apart - the muggier one is genuinely more dangerous. It is also why occupational guidance uses a combined measure called WBGT, which folds in humidity and radiant heat rather than air temperature alone; for most physical work, strain becomes likely once WBGT passes roughly 25°C.
There is a common myth worth clearing up. UK law sets no maximum working temperature. The Workplace (Health, Safety and Welfare) Regulations 1992 require a “reasonable” temperature indoors, and the Approved Code of Practice suggests a floor of around 16°C, or 13°C for strenuous work - but the HSE deliberately sets no ceiling, precisely because places like kitchens and bakeries are hot by their very nature. That does not let anyone off the hook. Employers still carry a legal duty to assess and control the risk, and in June 2026 the HSE reminded businesses that risks from extreme heat must be actively managed. The absence of a magic number simply means the responsibility sits with sensible risk assessment rather than a thermostat reading.
The performance cost is real and it arrives before the medical one. Studies of hot workplaces show that heat stress measurably slows reaction time and blunts concentration and attention. Lose as little as two per cent of your body weight in fluid - easily done across a hot double - and errors in judgement and coordination climb. In a kitchen full of blades, hot oil and heavy pans, a dulled mind and a slower hand are not a comfort problem; they are a safety problem. Heat does not just make people uncomfortable, it makes them slower, clumsier and more likely to be hurt.
Because so much of the heat is generated by the cooking itself, extraction is the single biggest lever most kitchens have. A well-designed canopy and duct system pulls hot air, steam and combustion by-products out of the room and replaces them with cooler, drier make-up air - directly lowering both the air temperature and the humidity that make sweating useless. When that system is clogged with grease or poorly balanced, its ability to shift heat drops away, and the room grows hotter, stickier and harder to work in. Extraction performance can also fall on gusty days, when wind pressure disrupts the flow at the flue, so a system already running below par has even less in reserve. Keeping the ductwork clean and the airflow properly balanced is one of the most effective heat-control measures a kitchen can invest in, and it protects fire safety at the same time.
Alongside good ventilation, the human measures are straightforward and well proven. Encourage frequent drinking rather than waiting for thirst, since thirst lags behind the fluid you have already lost - matching intake to sweat loss keeps people out of the danger zone. Rotate staff off the hottest stations, build in more and shorter breaks during heatwaves, and give new starters time to acclimatise instead of throwing them straight onto the grill in July. Lighter, breathable uniforms help the body do its own cooling. Train the team to recognise the early signs in themselves and each other, and to treat confusion, collapse or hot dry skin as the emergency it is - move the person somewhere cool, cool them actively and call 999. None of this is exotic. It is simply respecting what the body is quietly telling you long before it shouts.
Questions
Your body aims to hold a core temperature of around 37°C. For a sustained eight-hour shift it should stay below 38°C; once it climbs past 39°C the risk of acute heat illness such as heatstroke rises sharply. You cannot feel your exact core temperature, which is why the warning signs and sensible controls matter more than any single reading.
No. UK law sets no maximum working temperature. The Workplace (Health, Safety and Welfare) Regulations 1992 require a reasonable temperature indoors, with a suggested minimum of around 16°C, or 13°C for strenuous work, but no upper limit - partly because kitchens are hot by nature. Employers still have a firm legal duty to assess and control heat risk through good ventilation, breaks, hydration and sensible scheduling.
Sweating only cools you when the sweat evaporates. In the damp, steamy air of a kitchen, sweat cannot evaporate easily, so it drips off without carrying heat away while you still lose fluid and salts. That means two kitchens at the same air temperature can be very different, with the muggier one far harder on the body. Good extraction that removes steam and lowers humidity is one of the most effective ways to reduce that strain.
Heat measurably slows reaction time and dulls concentration and judgement before any medical symptoms appear. Losing as little as two per cent of your body weight in fluid increases errors in coordination and decision-making. In a room full of knives, hot oil and heavy pans, a slower hand and a foggy mind translate directly into cuts, burns and slips, so heat stress is a genuine accident risk as well as a health one.
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