Phoenix Journal · LEV Testing
When staff keep finishing shifts with headaches, the air they are breathing is usually the cause. Here is how poor ventilation, cooking fumes and CO2 build-up trigger it - and how LEV testing proves what is going wrong.
Air quality & staff wellbeing
If your team keeps finishing shifts with a dull, throbbing headache, the air they are breathing is usually the first place to look - not the paracetamol drawer.
Headaches that cluster around one room, one shift pattern or one time of day are rarely a coincidence. In busy commercial kitchens and back-of-house spaces, the most common culprit is stale, poorly ventilated air loaded with cooking fumes, combustion gases and a slow build-up of carbon dioxide. When the extraction and fresh-air supply cannot keep pace with the heat and the number of people in the room, the symptoms show up in your staff long before anything trips an alarm.
The good news is that this is measurable, and it is fixable. UK law already sets clear expectations for the air in an occupied workplace, and there are recognised thresholds that tell you whether a space is comfortably ventilated or quietly making people unwell. Understanding those numbers is the difference between guessing and knowing.
A headache is a blunt symptom with a lot of possible causes, but in a working kitchen or a busy enclosed space a handful of factors come up again and again. Getting to the real reason means thinking about what your people are breathing and how quickly that air is being replaced.
What ties most of these together is airflow. When extraction is weak, blocked with grease, or simply overwhelmed, contaminants that should be pulled straight outside instead linger at head height. That is why headaches so often track with the busiest services and the hottest days - exactly when the system is under the most strain.
The numbers that matter
These are the reference points UK employers are measured against. They turn a vague complaint about "stuffy air" into something you can test, record and act on.
Under the Workplace (Health, Safety and Welfare) Regulations 1992, every enclosed workplace must have effective and suitable ventilation, and Approved Document F of the Building Regulations sets out the fresh-air supply that a space is expected to provide. As a benchmark, fresh-air rates should not normally fall below 5 to 8 litres per second per person, with around 10 litres per second per person recommended for most commercial settings. If your room is packed and the air-change rate is low, the maths simply does not add up - and your staff feel the shortfall.
Once you accept that the air is the likely cause, the path forward is refreshingly practical. You do not have to live with a workforce that clocks off feeling rough.
Start by measuring. A simple CO₂ monitor placed at head height in the worst-affected area, logged across a full shift, will tell you very quickly whether ventilation is keeping up. Steady readings drifting past 1500 ppm during service are a clear flag. Pair that with a look at the physical system - are the canopy filters clean, is the extract fan actually moving the air it should, and is the ductwork clear rather than caked in grease? A system that looks fine at a glance can be moving a fraction of its designed airflow once the ducting is fouled.
Two failures in particular tend to sit behind headache complaints. The first is fumes that are visibly not being pulled away - if you are wondering why smoke keeps filling your kitchen during service, that same lost capture is dumping combustion gases and irritants straight into your team's breathing zone. The second is a failing extract fan: if you have noticed your roof fan vibrating, it may be running well below its rated performance, quietly starving the whole system of airflow long before it finally stops.
The formal, legally recognised way to confirm your extraction is doing its job is a thorough examination and test of the local exhaust ventilation (LEV) system. Carried out by a competent person to the HSE's HSG258 guidance, it measures capture and duct velocities at each hood, checks fan performance and filter condition, and compares the results against the system's design intent. Anything underperforming is identified with the numbers to prove it, and the records - which must be kept for at least five years - give you a documented trail that the air your staff breathe is actually being controlled. It is also a legal duty: COSHH Regulation 9 requires that test at least every 14 months, and enforcement follows for those who let it lapse.
Questions
Yes. When extraction and fresh-air supply cannot keep pace with the heat and the number of people in a room, carbon dioxide, combustion gases and cooking fumes build up in the air your team breathes. Long spells above roughly 1000 ppm of CO2 are commonly linked to headaches, tiredness and poor concentration, and low-level carbon monoxide adds nausea to the mix. It is one of the most common and most overlooked causes of clustered headache complaints at work.
Look for a pattern. Headaches that cluster in one room, spike during the busiest services or worsen on hot days point strongly to ventilation rather than individual health. A CO2 monitor placed at head height and logged across a full shift gives you an objective answer quickly - readings that drift past 1500 ppm during service are a clear sign the space is under-ventilated and action is needed.
CO2 below 800 ppm indicates a well-ventilated space, while readings consistently above 1500 ppm signal poor ventilation. For carbon monoxide, the HSE sets a workplace exposure limit of 30 ppm averaged over eight hours and 200 ppm over any 15-minute period. The Workplace (Health, Safety and Welfare) Regulations 1992 also require effective and suitable ventilation in every enclosed workplace.
Under COSHH Regulation 9, a local exhaust ventilation system must have a thorough examination and test at least every 14 months, carried out by a competent person to the HSE's HSG258 guidance. Higher-risk processes may need it more often. The test measures capture and duct velocities, checks fan and filter performance, and the records must be kept for at least five years.
Phoenix Duct Clean · by the numbers
Phoenix examines and tests local exhaust ventilation to HSG258 and COSHH - measured, reported and certificated, UK-wide.