Three duct types
A mixed-use building often stacks offices or flats over a commercial kitchen. That puts two very different duct systems in one structure - the office air system and the kitchen's grease riser - each needing its own clean and standard.
The short answer
Mixed-use buildings routinely put offices or flats directly above a restaurant or takeaway. That stacks two completely different ventilation systems into one structure: the upper floors have their own general air system, cleaned for air quality under TR19 Air, while the kitchen below has a grease extract that usually runs up through the building to a rooftop fan, cleaned for fire risk under TR19 Grease. They look like one building problem but they are two jobs with two standards - and confusing them leaves a gap.
The office air system
The ventilation serving offices and flats is a dry, general system - supply and extract moving fresh and stale air, with no grease in it. It is governed by TR19 Air and BS EN 15780, which classify cleanliness by the use of the space: general office and residential environments fall in the medium class, cleaned when dust accumulation passes the threshold rather than on a fixed date. Neglected, it harbours dust, pollen, bacteria and mould and circulates them through the workspace, restricts airflow, and drives up heating and cooling costs. The employer's duty under the Workplace (Health, Safety and Welfare) Regulations to provide adequate ventilation sits behind it.
This is the system that gets forgotten, because with no flames or grease to force the issue it drifts. In a mixed-use building it is easy for an office tenant to assume the building's ductwork is someone else's responsibility, when their own air system needs its own survey.
The kitchen grease riser
The kitchen's grease extract is a different animal entirely. It carries combustible grease-laden air, and in a stacked building it commonly runs as a vertical riser up through or alongside the upper floors to discharge at roof level. That riser is governed by TR19 Grease on a use-based cleaning cadence, and it matters to the offices above even though it is not their duct: a grease fire in a neglected riser can travel upward through the building and threaten the floors it passes. Standards prefer grease risers to be fire-rated duct or run in a protected shaft precisely so a fire cannot break out into occupied space.
For an office tenant the practical point is to know which duct is which. Your clean is the dry air system; the grease riser is the landlord's or the kitchen operator's responsibility - but its condition is part of your building's fire safety, so it belongs in the coordinating fire risk assessment.
Getting both covered
The clean answer in a mixed-use building is to treat the two systems explicitly. The upper-floor air ductwork gets a TR19 Air survey and clean to the medium class, with a post-clean report. The kitchen grease extract gets its TR19 Grease clean of the whole run - canopy, riser and rooftop fan - on its use band, with a certificate. A coordinating fire risk assessment for the whole building ties both records together so a landlord, insurer or fire officer can see the grease riser and the office ventilation are each maintained. Done together, in one visit, the two never fall into the gap between them.
Questions
The offices have their own general air ventilation, cleaned for air quality under TR19 Air, while the kitchen below has a grease extract cleaned for fire risk under TR19 Grease. They are two systems with two standards.
TR19 Air and BS EN 15780. General office and residential spaces fall in the medium cleanliness class, cleaned when dust accumulation passes the threshold rather than on a fixed date.
In a stacked building the grease extract usually runs up through or alongside the upper floors to the roof. A grease fire in a neglected riser can travel upward and threaten the floors it passes, so its condition is part of the whole building's fire safety.
Typically the office tenant's air system is their concern, while the grease riser is the landlord's or kitchen operator's. A coordinating fire risk assessment should tie both records together for the whole building.
Yes. The office air ductwork is surveyed and cleaned to TR19 Air and the kitchen grease extract to TR19 Grease in one coordinated visit, each with its own certificate.
Phoenix Duct Clean · by the numbers
We clean the office air ductwork to TR19 Air and the kitchen grease extract to TR19 Grease, with certificates for each. Call to sort both in one visit.