Duct cleaning & ventilation hygiene
Most buildings run several distinct extract systems, each with its own purpose, standard and maintenance duty. Knowing which is which is the difference between quietly compliant and quietly not.
Ask a facilities manager to describe their extract systems and the answer is often just kitchen extract, because that is the one everyone worries about. But most commercial buildings run several distinct extract systems, each with its own purpose, its own standard and its own maintenance duty. Knowing which is which, and what each one demands, is the difference between a building that is quietly compliant and one that is quietly not.
Extract ventilation is any system that pulls air out of a space, and a typical commercial building has more than one kind. There is general extract that removes stale air from offices, toilets and circulation spaces; there is kitchen grease extract that removes heat and grease-laden air from cooking; and there is process extract, or local exhaust ventilation, that captures a specific hazardous contaminant at its source. They look superficially similar, ducts and fans moving air, but they exist for different reasons, are held to different standards, and carry different legal obligations. Treating them all as one thing is where compliance quietly slips.
Knowing the three kinds
General extract handles routine air removal from toilets, changing rooms, plant spaces and general occupied areas. Its job is comfort and basic air quality, and its hygiene falls under the general ventilation cleanliness regime set out in BESA's TR19 Air, published in 2024, which classifies systems by the sensitivity of the space they serve and sets inspection and cleaning on that risk basis. Kitchen grease extract is a category of its own because grease is a fire hazard: it is governed by TR19 Grease, the 2019 specification for fire risk management of grease accumulation in kitchen extraction systems, and cleaned to keep grease below the levels at which it becomes a fire risk.
Process extract, or local exhaust ventilation, is different again. LEV captures airborne contaminants, dust, mist, fume, vapour, at the point they are generated, before workers can breathe them in, and it exists to control exposure to substances hazardous to health. It carries the heaviest statutory weight of the three: under the relevant health and safety regulations, an LEV system must receive a thorough examination and test by a competent person at least every fourteen months, follow the HSE's HSG258 guidance on controlling airborne contaminants, and keep a logbook of checks and results. Miss that fourteen-month examination and the building is in breach, regardless of how clean the ductwork looks.
These systems also sit within a wider family of supply and extract arrangements. A building may use extract-only ventilation, which pulls stale air out and lets fresh air in through gaps and inlets, creating a slight negative pressure useful where you want to contain odours; supply-only, which pushes filtered fresh air in; or balanced systems that control both. Understanding which arrangement serves which space tells a facilities manager where the pressure relationships matter and where a fault in one system will show up as a problem in another.
What the FM actually owns
For the facilities manager, the practical duty is threefold: know which extract systems the building has, know which standard governs each, and keep the records that prove each one is maintained. That means competent contractors for cleaning and testing, photographic and documented evidence of the work, and a schedule that reflects each system's own requirement, annual-ish inspection for general hygiene, risk-based cleaning frequency for kitchen grease, and the fixed fourteen-month cycle for LEV. Insurers and enforcement bodies increasingly ask for that evidence, and it forms part of the broader bundle of paperwork covered in the compliance documents every FM should keep. The records are not bureaucracy for its own sake; they are the proof that the duty has been met.
Bringing it together
The useful mental model is that a building does not have an extract system, it has a portfolio of them, and each line in that portfolio has an owner, a standard and a schedule. Map them out, assign the right cleaning and testing regime to each, keep the evidence, and the whole thing becomes manageable rather than a source of nasty surprises at inspection. Get the kitchen grease system onto a proper risk-based frequency, keep the general systems inspected, keep the LEV examinations on their fourteen-month clock, and the building stays genuinely compliant. It is the same evidence-led discipline that decides how often office ventilation should be cleaned, applied across every extract system at once.
Questions
Usually several. A typical commercial building runs general extract for offices, toilets and circulation spaces; kitchen grease extract for cooking; and process extract, or local exhaust ventilation, for specific hazardous contaminants. They look similar but serve different purposes and carry different obligations.
General extract hygiene falls under BESA's TR19 Air, which classifies systems by risk. Kitchen grease extract is governed by TR19 Grease for fire risk management. Process LEV follows the HSE's HSG258 guidance and carries statutory health and safety duties for controlling exposure.
Local exhaust ventilation captures hazardous contaminants at source to control worker exposure, and it carries the heaviest statutory weight. It must receive a thorough examination and test by a competent person at least every fourteen months, follow HSG258, and keep a logbook of checks and results.
Extract-only pulls stale air out and lets fresh air in through gaps, creating slight negative pressure useful for containing odours. Supply-only pushes filtered fresh air in. Balanced systems control both. Knowing which serves which space tells you where pressure relationships matter.
Evidence that each extract system is maintained to its own standard: competent contractors, photographic and documented proof of cleaning and testing, and a schedule reflecting each system's requirement, risk-based frequency for kitchen grease, regular inspection for general hygiene, and the fixed fourteen-month cycle for LEV.
Phoenix Duct Clean · by the numbers
Each type has its own standard and schedule. Talk to Phoenix about cleaning and documenting your general, kitchen and process extract systems to the right specification.