Fire Protection for Common Grease Ducts
By Jeff Nocent, P.Eng. (O’Dell Toronto Office)
Working with SpringAir Systems, O’Dell offers complete design and installation services for kitchen fire suppression systems. On any project where we are supplying hoods and fire suppression, we will provide stamped engineering drawings at no additional cost. All you have to do is ask.
In larger institutional kitchens, there are often multiple hoods connected to a single exhaust fan through a common grease duct system. Common grease ducts present fire suppression challenges, requiring special attention by the engineer.
A review of the following NFPA standards provides guidance on how to address common grease ducts.
NFPA 96: Standard for Ventilation Control and Fire Protection of Commercial Kitchen Operations
- Kitchen hoods, makeup air, discharge requirements
- Grease duct construction, clearances
NFPA 17A: Standard for Wet Chemical Extinguishing Systems
- Wet chemical protection methods, coverage areas
In general, grease ducts require additional fire protection when one of the following two conditions exist:
- Hoods from two or more separate tenants are connected to a common grease duct system.
- Long grease duct runs where the hood collar nozzle will not provide enough coverage area to protect the grease duct. This can occur with one hood if the grease duct run is long enough.
There are two methods available for addressing these conditions. The table below outlines each approach and their inherent pros and cons:
All Hoods Fire Suppression Systems Discharge
Single Hood/Tenant and Common Grease Duct Systems Discharge
|Summary of Components|
|When any single detector or manual pull station is activated:
||When any single detector or manual pull station is activated: