Phoenix Journal · Ductwork
Most extract failures signal weeks before they stop the kitchen. Monitoring the fan, filters and airflow catches that signal early - turning expensive emergency callouts into quiet, planned maintenance.
Monitoring & maintenance
The cheapest emergency callout is the one you never had to make - and in a commercial kitchen, that usually comes down to knowing your extract system is struggling before it stops.
Most extraction failures do not arrive out of the blue. A fan bearing runs a little rougher for weeks, a motor draws a fraction more current, grease loads the ductwork until the fan is fighting for air, and the filters choke quietly behind the canopy. None of it is visible from the pass. The first anyone tends to notice is smoke hanging over the line on a Friday service, a gas interlock that will not prove, or a fan that simply refuses to start - and by then you are paying weekend rates for an engineer and, worse, sending staff home.
Monitoring changes the order of events. Instead of the kitchen telling you something is wrong when it is already too late, sensors on the fan, the ductwork and the filters give you weeks of warning while everything is still running. That gap between the early signal and the actual failure is where emergency callouts turn into planned, quiet, off-peak visits. This is how it works in practice, and where it pays for itself.
The value is not in the sensors themselves - it is in the fact that a rotating fan gives itself away long before it stops. Every fan has a vibration signature, and that signature shifts as a bearing wears or an impeller loads with grease, usually weeks before the motor gets hot or makes any noise a person could hear from the kitchen. A small vibration and temperature sensor on the fan housing picks that up continuously. Alongside it, three other readings tell the same story from different angles:
Put together, these give you the two things reactive maintenance never can - a direction of travel, and time. You are no longer asking whether the system is broken today; you are watching how fast it is heading that way.
To see why monitoring cuts callouts, it helps to look at what causes them. In a kitchen extract system, the two culprits behind most unplanned failures are grease and neglect of the moving parts - and they feed each other.
Grease is the obvious one. Every hour of frying and grilling carries fat into the canopy, through the filters and along the ductwork toward the fan. Left to build, it does three things at once: it becomes a serious fire load, it narrows the duct so the fan has to work harder, and it coats the impeller so the fan runs out of balance. That is precisely why the industry guidance for cleaning grease extract systems - the BESA standard commonly referred to as TR19 Grease - exists, and why insurers increasingly ask for evidence that the system is cleaned to a measured standard. A system that is quietly filling with grease is a system building toward a callout, whether that callout is a tripped fan, a failed interlock or a fire.
The moving parts are the quieter culprit. Fan bearings wear, belts slacken, motors age. On a reactive regime none of this is looked at until it stops, so the failure lands at the worst possible moment - during service, at full load, on the day the kitchen can least afford it. Monitoring attacks both problems from the same direction. Rising current and vibration flag the grease and wear early, so the deep clean and the bearing change get booked into a quiet morning instead of erupting on a Saturday night. It also sharpens the cleaning itself - instead of cleaning to a fixed interval and hoping, you clean when the readings say the ductwork has genuinely loaded, which is the same condition-led logic behind good energy monitoring that keeps fan running costs down rather than letting a straining motor waste power around the clock.
The financial case is straightforward once you separate the two types of visit. An emergency callout is expensive in ways that never show on the invoice alone: out-of-hours engineer rates, express parts, and the real cost - a kitchen that cannot open or has to run on reduced covers while the extract is down. A planned visit costs a fraction of that, because it happens on your terms, during a closure or a quiet weekday, with the right parts already on the van. Monitoring is simply the tool that moves work from the first column to the second. Operators running structured condition monitoring into a maintenance system have reported unplanned downtime falling by up to 45% and overall maintenance spend dropping by around a third in the first year - not because they do less work, but because the work stops being emergency work.
There is a compliance dividend too. Since the gas standards were updated, IGEM/UP/19 sets carbon dioxide interlocking as the minimum ventilation check for new commercial kitchen installations, sitting alongside air differential pressure switches or fan current monitoring under BS 6173. In other words, the direction of travel in the regulations is already toward continuous, sensed proof that ventilation is working - not an annual tick in a book. Feeding that same CO₂ and airflow data into a monitoring dashboard, as covered in our guide to using CO₂ as a proxy for ventilation quality, means the safety interlock and the maintenance system are reading from the same instruments, and you get an early warning and a compliance record from one set of sensors.
None of this replaces a competent engineer or a proper deep clean - it aims them. Monitoring tells you which fan to look at, which duct run has loaded, and when the filters are actually spent, so every visit is doing something the data has already justified. The result is fewer surprises, a system that runs efficiently instead of straining, and a maintenance budget you can plan rather than react to.
Questions
The core readings are fan vibration, motor current, the differential pressure across the filters, and the airflow proving signal at the gas interlock. Each one shifts gradually as a bearing wears or the ductwork loads with grease, so together they show the direction the system is heading. That lets you act on a trend rather than waiting for an outright failure.
A rotating fan typically changes its vibration signature and current draw weeks before it stops - commonly three to six weeks of usable warning. That gap is the whole point: it is long enough to book a planned visit during a closure or a quiet weekday instead of paying out-of-hours emergency rates mid-service. The earlier the signal, the cheaper and calmer the fix.
No - it aims it. Monitoring tells you when the ductwork has genuinely loaded up and which fan is under strain, but you still need a competent clean to the BESA TR19 Grease standard to remove the grease, reset the fire risk and restore airflow. Used together, you clean when the readings justify it rather than guessing from a fixed calendar, which usually means the right work at the right time.
Phoenix Duct Clean · by the numbers
Phoenix surveys and cleans kitchen and building ductwork to the TR19 standard - measured, cleaned and certificated, UK-wide.