Phoenix Journal · Extraction
Water beading under a commercial kitchen canopy is a ventilation warning, not a housekeeping chore. Here is how to trace it back to the balance of extract, make-up air and surface temperature - and put it right.
Kitchen extraction · condensation
Water dripping off the underside of a canopy is not just a nuisance to mop up - it is your ventilation telling you the balance between extract, supply air and surface temperature has slipped out of true.
Condensation forms whenever warm, moisture-laden air meets a surface that sits below its dew point. A commercial kitchen produces that warm, wet air by the bucketload: boiling pans, steamers, bains marie, dishwashers and open ranges all pour water vapour into the space, and much of it is drawn straight up towards the canopy. If the steel above the line meets air that is cooler than the vapour it is carrying, the moisture gives up its heat and turns back to liquid on the metal. So when you see beads gathering on the underside of your canopy, the question is rarely "why is there moisture?" - the moisture is a given - it is "why is that surface cold enough to catch it?"
The answer almost always comes down to the interaction of four things: how much air you are extracting, how much fresh air is being let back in to replace it, how warm that replacement air is, and how well the canopy itself is insulated. Work through those in order and the cause tends to reveal itself. Below is the diagnostic sequence a competent engineer follows on site, framed so you can carry out the first checks yourself.
It is tempting to treat canopy condensation as a housekeeping problem - wipe it down, put a bucket underneath, carry on. That misses the point. Standing water on and around a canopy sits in exactly the warm, greasy conditions that let bacteria such as salmonella multiply, and it drips onto surfaces and food below. Left unchecked, the same moisture rots fixings, corrodes the stainless steel from the inside of seams outward, and shortens the life of an expensive piece of equipment. Persistent damp also stains ceilings, lifts paint and, where it tracks into electrics or light fittings, becomes a genuine safety hazard.
There is a compliance dimension too. Under the Workplace (Health, Safety and Welfare) Regulations 1992 and the guidance in HSE's catering sheets, you are expected to provide effective and suitable ventilation, and BS 6173 governs the safe installation of gas catering appliances. That last point matters more than it first appears: an extract running without enough make-up air pulls the kitchen into negative pressure, and negative pressure can disturb the flues on gas equipment, drawing combustion products - including carbon dioxide, CO₂, and worse, carbon monoxide - back into the room. The cold, draughty conditions that produce condensation are often the same conditions that put the gas installation at risk, which is why an engineer treats dripping steel as a symptom worth chasing rather than a cosmetic annoyance.
The practical fix depends on which step above flagged the fault. Sometimes it is as simple as commissioning the make-up air unit correctly, replacing a failed heater battery, or re-balancing the extract to its design velocity. Just as often the trigger is a canopy that has not been cleaned to standard, where grease and blocked filters have quietly strangled the airflow the whole system depends on. Getting the extraction professionally stripped, degreased and re-balanced restores the airflow paths, removes the cold stagnant pockets, and lets a properly tempered supply do its job.
Canopy design itself can also be the root cause. A wall-mounted canopy, an island canopy and a condense canopy each handle moisture differently, and putting a steam-heavy appliance under the wrong style leaves you fighting condensation forever. If your problem is worst over the wettest equipment, the guide to choosing between a wall, island or condense canopy will help you see whether the canopy was ever the right tool for the job.
Reduced to its essence, a dry canopy is a balanced canopy: extract matched to the cooking load, replacement air matched to the extract, and that replacement air warm enough that no surface it touches ever falls to the dew point. When one of those three drifts, the steel goes cold and the water appears. Keeping the canopy clean is what preserves the airflow the balance relies on, which is why regular, thorough extraction cleaning is the single most reliable defence against condensation returning.
Questions
It is both. The standing water sits in warm, greasy conditions that let bacteria such as salmonella grow and then drips onto surfaces and food below, and over time it corrodes the steel and can track into electrics. It is also often a sign the make-up air balance is wrong, which in a gas kitchen can disturb appliance flues, so it is worth investigating rather than just mopping up.
Frequently, yes. Blocked baffle filters and grease-choked plenums throttle the airflow the whole system relies on, creating cold, stagnant pockets where vapour settles. A thorough professional degrease and re-balance restores those airflow paths and removes the standing conditions, though if the root cause is a failed make-up air heater or an undersized supply, that will need addressing too.
There is no single figure, because it depends on how humid the air is - condensation appears whenever a surface drops below the dew point of the air touching it. In a busy kitchen full of steam the dew point can be high, so even mildly cool make-up air can trigger it. That is why DW/172 sets minimum supply temperatures of around 10 to 16 degrees Celsius, to keep surfaces warm enough to stay dry.
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.