Commercial kitchens can be a technical challenge and if the general contractor/ trades do not have much experience many construction issues may arise.  Below is a description of the such failures in hopes they may be avoided in the future.

Above is a photo of the kitchen exhaust system. The grease duct is on the left that carries the grease laden vapours and the kitchen exhaust fan on the right that expels the fumes upwardly and away from the building. Once we zoom in closer we see a few issues:


Locking washers are missing on bolts connecting the kitchen exhaust fan to the grease duct.

The issue is over time the vibration and heat may loosen the nuts causing it to disconnect and the kitchen exhaust fan not be capable to operate correctly. Further more NFPA-96-14 paragraph states:

In-line fans shall be connected to the exhaust duct by flanges securely bolted as shown in Figure through Figure or by a system specifically listed for such use. Figure clearly shows a locking washer between the bolt and flange.

Grease cup is missing on the underside of the kitchen exhaust fan allowing the grease to spill onto the roof.  Overtime this will cause damage to the roof and create a possible fire hazard.  Further NFPA-96 -14  paragraph sentence (4) states:

The ability to drain grease out of any traps or low points formed in the fan or duct near the termination of the system into a collection container that is noncombustible, closed, rainproof, and structurally sound for the service to which it is applied and that will not sustain combustion. 


Here we have a picture of the grease duct traveling up the side of the building and terminating on the roof.  The grease duct contains grease laden vapours and must be cleaned out every so often.

Due to the nature of accessing the grease duct one must have a number of access panels specifically located. Why is this important? If you do not have enough access points (every 12′, every elbow or turn in direction and every floor) the ASTTBC trade may not be able to properly cleaning the grease duct.  Thus exposing the grease duct, building and it occupants at risk to a fire.  NFPA-96-14 paragraph states:

Where personnel entry is not possible, adequate access for cleaning shall be provided on each floor.

In this case we are missing an access panel on the 2nd floor.

Inside the kitchen we have a hood and its backsplash panel.  The primary purpose of the hood is to capture and contain the products of combustion produce during the cooking operation such that it doesn’t enter the common space.

The other purpose is in the event of a fire the hood captures and contains the smoke and flames and exhausts it safety to the outdoors.  The issue in these pictures would be during a fire the cooking appliances and the hood will get very hot such that any combustible material within 18″ may catch fire. Cleary we see wood studs with drywall butt up against the right side of the hood. Further it is not complying with code; NFPA-96-14 paragraph 4.2.1 states:

…hoods, grease removal devices, exhaust fans, and ducts shall have a clearance of at least 457 mm (18 in.) to combustible material….

At the time of this blog the corrections were being made and the general contractor, client and architect were happy Evolve caught this deficiencies. End of the day we are hoping this was an informative blog for consultants, trades, etc.  Please share any feed back to us!

James Hicks P.Eng

Evolve Mechanical Solutions