Kitchen operations · Heat & ventilation
No invoice ever arrives for heat - it collects in slower tickets, climbing error rates and the chefs who quietly leave. What the law actually requires, and why the fix is usually hanging over the line already.
The invisible payroll cost
Nobody budgets for heat, but every hot kitchen pays for it. The costs hide in places the P&L does not itemise: tickets that take longer as the shift wears on, error rates that climb with the temperature, breaks that stretch, agency shifts to cover the chef who went home dizzy, and the slow leak of good staff to the cooler kitchen down the road. Heat is a productivity tax collected in minutes and mistakes, which is exactly why it survives - no single invoice ever arrives for it.
The physiology is not controversial. As temperatures climb, the body diverts effort to cooling itself: heart rate rises, concentration drops, reaction time lengthens, and fine motor work - knife work, plating, reading a ticket correctly - degrades first. The Health and Safety Executive lists the consequences of unmanaged heat as fatigue, loss of concentration and, at the far end, heat exhaustion and heat stroke. Long before anyone collapses, the kitchen is already slower, clumsier and more dangerous around fryers, blades and wet floors than the same brigade at a workable temperature.
What the law actually says
A persistent kitchen myth says staff can walk out above some magic number. There is no legal maximum workplace temperature in the UK. What exists instead is a duty: the Workplace (Health, Safety and Welfare) Regulations 1992 require employers to provide a reasonable indoor temperature, and the Management of Health and Safety at Work Regulations require the risk - including heat stress - to be assessed and controlled. HSE's guidance is explicit that air temperature alone is not the measure; thermal comfort turns on six factors together - air temperature, radiant heat from equipment, humidity, air movement, clothing and work rate - and a kitchen scores badly on all six at once: radiant heat from the line, steam from pots and wash-up, chef whites, and sustained physical work.
That framing matters commercially, because it points at the fixes. Of the six factors, a kitchen can rarely change the clothing or the work rate, but it can change air movement and the heat load - and both run straight through the ventilation. HSE's own hierarchy for heat says remove or reduce the heat source and control the temperature with engineering solutions first, before resting on breaks and water. In a commercial kitchen, the engineering solution already exists: it is bolted to the ceiling, and the only question is whether it is still doing what it was designed to do.
Finding the lost airflow
When a kitchen that used to be bearable becomes brutal, the appliances have usually not changed - the air has. Grease loading in the canopy plenum, filters and ductwork chokes the system gradually, and a heavily loaded extract can be running 30 to 50 per cent down on its design airflow. The heat the system was engineered to remove stays in the room instead, along with the smoke and moisture that make it feel worse than the thermometer says. Because the decline is gradual, the brigade normalises it season by season - until a heatwave lands on top of an already-crippled system and the kitchen becomes unworkable in an afternoon.
The diagnostic sequence is short. Check the filters are clean and actually fitted - missing baffles dump grease straight into the duct. Ask when the system last had a proper clean through the full duct run and fan, not a canopy wipe, and compare that against the interval a kitchen of your intensity actually needs - heavy-use sites sit around three months under TR19 Grease guidance. Confirm the make-up air path is open: extract cannot remove air the building will not replace, and blocked supply grilles quietly strangle the whole system. And check the fan itself - a slipping belt or a grease-caked impeller can halve performance while sounding almost normal.
Then do the arithmetic that makes the case. A brigade of six on a hot line, each losing even ten per cent of their effective output to heat across a 40-hour week, is two and a half working days of paid labour evaporating weekly - before counting mistakes, wastage, sickness and turnover. Against that, restoring the ventilation to design performance is not a maintenance cost. It is one of the few investments in a kitchen that pays back in payroll, safety and staff retention simultaneously.
Questions
No. UK law sets no maximum workplace temperature. Employers must provide a 'reasonable' temperature under the Workplace Regulations 1992 and assess and control heat stress risk. HSE guidance treats thermal comfort as six factors together - air temperature, radiant heat, humidity, air movement, clothing and work rate - not a single number on a thermometer.
Usually because the extraction has degraded, not because the kitchen changed. Grease loading in filters, ductwork and the fan can cut airflow by 30 to 50 per cent, leaving heat the system was designed to remove hanging over the line. Blocked make-up air paths and worn fan components produce the same effect.
Follow HSE's hierarchy: engineering controls before behavioural ones. Clean or refit the grease filters, restore the full extract system to design airflow with a measured TR19 Grease clean, open up the make-up air path, and service the fan. Water, breaks and fans help people cope - restored extraction removes the heat itself.
Phoenix Duct Clean · by the numbers
The heat is usually lost airflow. We survey and clean extract systems to TR19 Grease, restoring design performance - overnight, with no extra charge for out-of-hours.