Kitchen Exhaust
Kitchen exhaust cleaning is a fire safety requirement rather than a housekeeping one, and the part that matters most is the part nobody can see.
Short answer
Grease accumulates through the entire exhaust system — hood, filters, duct, riser and rooftop fan — and it is the fuel in a kitchen exhaust fire. A proper clean is to bare metal through the whole run, not a hood wipe. The vertical riser is the part most often skipped and the part with the most grease.
What has to be cleaned
The hood interior and the grease filters or baffles.
The plenum behind the filters.
The horizontal duct run.
The vertical riser, which is the part most frequently skipped on a cheap contract and which holds the most grease.
The rooftop fan, including the fan blades, the housing and the grease containment.
And access panels cut and properly closed where the duct has none, which on an older Toronto installation it frequently does not.
Bare metal, not wiped
The standard is clean to bare metal. A hood that looks clean with a coating of grease still on the duct behind it has not been cleaned, it has been wiped. Ask for before and after photographs of the riser and the fan specifically, because that is where the difference between the two contracts shows.
The frequency question
Set by the cooking volume and the type of cooking rather than by a calendar.
Solid fuel and high-volume frying need it far more often than a low-volume operation.
The applicable standards specify inspection frequencies by cooking type, which the contractor should be working to.
Fire code enforcement and the insurer both take an interest, and both ask for records.
A cheap annual contract on a high-volume kitchen is not compliance, it is paperwork.
And between cleanings, filter cleaning and hood wiping is kitchen staff work and is what keeps the interval achievable.
The related items
Make-up air, which has to balance the exhaust. A kitchen under heavy negative pressure pulls air from every gap in the building, which is both an odour complaint and a backdraft risk on gas appliances.
The fire suppression system, which has its own inspection schedule and which must not be damaged during cleaning.
The rooftop discharge position relative to intakes and neighbouring tenants, which is the odour complaint source.
The fan belt, bearings and speed, because a slowing fan reduces capture before anybody notices a smell.
The grease containment at the fan, which if it overflows stains the roof and degrades the membrane.
And the records: date, scope, photographs and the technician certification, which is what the fire inspector and the insurer ask for.
Common questions
What is most often skipped?
The vertical riser and the rooftop fan. Ask for photographs of both.
How often is it needed?
By cooking volume and type rather than by calendar. High-volume frying needs it far more often.
Why does the kitchen smell reach the tenants upstairs?
Usually make-up air imbalance, a duct leak in a shaft, or rooftop discharge near their intake.