Section 505.1/Commercial Kitchen Hood Requirements
IMC 505 covers Type I and Type II commercial kitchen hood requirements including size, mounting height, makeup air, and fire suppression system coordination.
Commercial cooking equipment that produces grease-laden vapors must be provided with a Type I hood per Section 507.2. Equipment that produces heat, steam, or moisture but not grease (dishwashers, steamers) may use a Type II hood per Section 507.2.1. Type I hoods must extend at least 6 inches beyond the cooking equipment on all open sides (Section 507.2.5) and be mounted with the lower edge not more than 6.5 feet above the floor unless the hood is a listed type with specific mounting requirements. Type I hoods must be connected to a dedicated exhaust system with grease-rated ductwork (minimum 16-gauge steel, welded seams, no screws). The exhaust rate must meet the minimum CFM per linear foot of hood from Table 507.2.1 based on hood type (wall canopy, island canopy, proximity, or backshelf). Makeup air must be provided to replace the exhausted air, delivered to the kitchen space without short-circuiting the hood capture. Type I hoods must have a fire suppression system (wet chemical) per NFPA 96 protecting the cooking equipment, hood, and duct.
Why this section exists
Commercial kitchen fires are one of the most common sources of building fires. Grease accumulation in hoods and ducts provides a continuous fuel source, and cooking equipment provides the ignition source. The Type I hood captures grease-laden vapors before they deposit on building surfaces and HVAC equipment. The grease-rated ductwork and fire suppression system contain and suppress a grease fire within the hood and duct system. Makeup air prevents negative pressure that can pull odors, smoke, and combustion products into the dining area and compromise the hood's capture performance. The hood overhang and mounting height requirements ensure the thermal plume from cooking equipment is captured effectively.
What plan reviewers look for
Plan reviewers check the kitchen equipment plan for the cooking equipment types and verify the correct hood type (Type I for grease-producing, Type II for steam/heat). They check the hood dimensions against the equipment layout for the 6-inch overhang. They verify the exhaust CFM meets Table 507.2.1 for the hood type and configuration. They check that makeup air is provided and that the delivery method does not short-circuit the hood. They verify the fire suppression system is shown on the fire protection plan and coordinated with the cooking equipment. They check that the exhaust duct is specified as grease-rated (welded steel, no combustible materials within 18 inches).