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An exhaust system consists of a hood or canopy, a fan and duct system, and grease-removal equipment.
Hoods
Hoods should be made of stainless or carbon steel or other approved fire-resistant material. They should extend completely over all equipment that produces grease-laden vapors.
Ducts
A duct system is a passageway that transmits grease-laden vapors to the outside. Ducts should consist of fire-resistant materials, be isolated from other exhaust or ventilation systems, and lead directly to the exterior. Qualified personnel should also maintain and clean ducts regularly.
Fans
Fans move air and grease-laden vapors to the duct system. Fans and motors should be Underwriters Laboratories (UL)-listed for use in grease-laden atmospheres and have blades of nonferrous metal, such as aluminum.
Grease filters and extractors
These systems help rid hoods of grease. Commercial cooking operations require metal filters. They should be UL-listed.
Clearances
Exhaust systems should meet the following clearance criteria:
- minimum of 18 inches from hoods and ducts to combustible material
- minimum of 6 inches to noncombustible material if duct is enclosed
- minimum of 10 inches from outlet to adjacent buildings
- minimum of 10 inches from outlet to air intakes, space permitting
» Next: Exhaust System Schematic |
Properly designed hood
A typical fan duct system
Fire wrap is an acceptable duct insulation
Hazardous accumulation of grease in the exhaust system
Hazardous accumulation of grease in the hood and duct
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