Phoenix Journal · Extraction
In a busy commercial kitchen, heat is not just uncomfortable - it is a health exposure that builds across every shift, and your extraction system is one of the few causes you can measure and put right.
Staff health & kitchen heat
A commercial kitchen runs hot by design, but the heat your team stands in is rarely just an inconvenience - it is a health exposure that builds quietly across every shift.
Ask most chefs about the heat and they will shrug it off as part of the job. That acceptance is exactly what makes it a hidden problem. Heat does not announce itself the way a wet floor or a sharp blade does. It works slowly - a bit more fatigue by the third hour, a headache that arrives with the dinner rush, concentration that slips just as the pans are at their busiest. None of it shows up as a single dramatic incident, so it rarely gets logged, and what does not get logged rarely gets fixed.
Yet the source of a great deal of that strain sits directly above the line: the extraction canopy and the ductwork behind it. When that system is clean, correctly balanced and pulling the volume it was designed for, it carries away radiant heat, combustion gases and moisture before your staff have to breathe them. When it is greasy, undersized or quietly failing, the kitchen becomes a sealed box that traps all three. This article looks at what that heat is actually doing to the people working under it, and why extraction is a health control as much as a fire and compliance one.
Thermal comfort is not a single number on a wall thermometer. The Health and Safety Executive is clear that it depends on six factors working together - air temperature, radiant heat from ovens and ranges, humidity, air movement, the clothing and PPE your team wears, and how hard they are physically working. A chef in whites, plating over an open flame at full pace, is carrying a heat load that a simple room reading will never capture. That is why the HSE measures thermal comfort not by degrees but by the number of employees complaining of discomfort.
The law treats this seriously even though it sets no legal maximum temperature. Under the Workplace (Health, Safety and Welfare) Regulations 1992, you must provide a reasonable temperature indoors, and under the Management of Health and Safety at Work Regulations 1999 you are required to assess the risks to your staff and act on them. Heat is a hazard like any other. In June 2026 the HSE reiterated that the risks to workers from extreme heat must be managed, and a kitchen generates its own extreme heat regardless of the weather outside.
The physical toll follows a predictable path. Early on it is dehydration and fatigue. Then concentration and judgement start to fade - the point at which knife injuries, burns and slips become far more likely. In the worst cases you move into heat exhaustion and, rarely, heat stroke, which is a medical emergency. Long before that, though, a persistently hot kitchen drives the everyday problems that quietly erode a business: short tempers, higher sickness absence, and the churn of staff who simply decide the environment is not worth it. In a sector already fighting to recruit and retain skilled people, an uncomfortable, badly ventilated kitchen is a competitive disadvantage you can feel every service.
Where heat risk is genuinely high, a wall thermometer is not enough. The recognised tool is a Wet Bulb Globe Temperature meter, which captures radiant heat and humidity as well as air temperature, giving a truer picture of the load on the body. A simple log of twice-daily readings in known hot spots - beside the range, at the pass - alongside a cooler control point tells you far more than a single glance at a thermostat ever will.
The air, not just the heat
Heat is the part your team feels, but it is not the only thing a struggling extraction system leaves behind. Gas ranges, chargrills and ovens are combustion appliances, and combustion produces carbon monoxide and nitrogen dioxide. Extraction is what stops those gases lingering at head height. When airflow drops, the concentration climbs - and both gases carry workplace exposure limits that are legally binding under the Control of Substances Hazardous to Health Regulations, published by the HSE in EH40/2005.
Those numbers matter because the early symptoms of low-level carbon monoxide and nitrogen dioxide exposure - headache, dizziness, nausea, tiredness - look almost identical to the effects of heat and a long shift. That overlap is precisely why the cause so often goes unrecognised. Staff assume they are simply tired or dehydrated when the real culprit is a canopy that is no longer moving the volume of air it was built to move, allowing combustion products to build up in the breathing zone across the course of a service.
A commercial kitchen ventilation system is designed to a specification - in the UK that is DW172, the Building Engineering Services Association standard for kitchen ventilation, working alongside BS 6173 for the safe installation of gas appliances. Between them they set out the airflow rates, canopy sizing and the gas interlock that shuts off the gas supply the moment ventilation fails. On paper it is a robust system. In practice its performance depends entirely on whether the ductwork and filters behind the canopy are kept clean.
Grease is the enemy of airflow. As it accumulates on filters, canopy plenums and the internal walls of the ductwork, it narrows the path the air has to travel and forces the fan to work against ever more resistance. The volume it can actually extract falls, often well below the design figure, and it falls gradually enough that nobody notices the day it stops coping. What your team notices instead is the symptom - a kitchen that feels hotter and closer than it used to, air that hangs, and the headaches and fatigue that come with it. The heat and the poor air quality are frequently the first visible sign that extraction performance has quietly degraded, and they often surface in patterns you can read directly in how poor extraction shows up in staff health records.
This is why regular, thorough cleaning of the whole system - not just the filters a team can reach, but the full run of ductwork to the fan - is a health measure and not merely a fire-prevention one. Restoring the ductwork to a clean condition restores the airflow, and restoring the airflow restores the two things your staff most need: heat carried away, and combustion gases cleared before they are breathed. A cleaned system also lets the fan run more efficiently and quietly, and keeps the gas interlock and the wider ventilation performing as designed. If your team is quietly struggling and you are wondering why your staff keep getting headaches at work, the extraction system is one of the first places worth looking, because it is one of the few causes you can measure, verify and put right.
The practical steps are straightforward. Keep a service record for the system so you can prove the state of the ductwork and its cleaning frequency. Watch for the soft signals - a warmer kitchen, complaints of stuffiness, staff reporting headaches at the same point in every shift - and treat them as data rather than grumbling. Match your cleaning interval to how hard the kitchen works, because a high-volume, gas-heavy operation soils its ductwork far faster than a light one. Get the airflow verified after cleaning, so you know the system is genuinely back to specification and not just visually cleaner. Do those things and the heat stops being an invisible cost carried by your people, and becomes something you actively control.
Questions
No, UK law does not set a specific maximum temperature for any workplace, including kitchens. However, the Workplace (Health, Safety and Welfare) Regulations 1992 require you to maintain a reasonable temperature, and the Management of Health and Safety at Work Regulations 1999 require you to assess and control heat as a hazard. The HSE judges thermal comfort by the number of staff complaining of discomfort rather than by a single temperature reading.
Sustained heat causes dehydration, fatigue and loss of concentration, which raises the risk of burns, cuts and slips, and in severe cases can lead to heat exhaustion or heat stroke. On top of that, weak extraction lets combustion gases such as carbon monoxide and nitrogen dioxide build up, producing headaches, dizziness and nausea. Because these symptoms mimic simple tiredness, the underlying cause is often missed.
The HSE publication EH40/2005 sets workplace exposure limits that are legally binding under the COSHH Regulations. Carbon monoxide has a long-term limit of 20 ppm as an eight-hour average, and nitrogen dioxide has a long-term limit of 0.5 ppm, which was tightened following the transitional period that ended in August 2023. Effective extraction is the main control that keeps kitchen air below these levels.
Grease building up on filters and inside ductwork narrows the airflow path and forces the fan to work harder, so the volume of air actually extracted falls below the design figure. This traps heat and combustion gases in the kitchen. A thorough clean of the whole system, from canopy to the full run of ductwork, restores the airflow so heat is carried away and gases are cleared before staff breathe them. It is worth verifying airflow after cleaning to confirm the system is back to specification.
Phoenix Duct Clean · by the numbers
The right kit only helps if the system stays clean. Phoenix degreases canopies, filters and ductwork to TR19 Grease - UK-wide, overnight.