506.3.5 Separation of grease duct system.
MC § 506.3.5
A separate grease duct system shall be provided for each Type I hood. Exceptions: 1. A separate grease duct system is not required where all of the following conditions are met: 1.1. All interconnected hoods are located within the same story, provided that they are part of the same facility and under the control of one owner or tenant. 1.2. All interconnected hoods are located within the same room or in adjoining rooms, provided that they are part of the same facility and under the control of one owner or tenant. 1.3. Interconnecting ducts do not penetrate assemblies required to be fire-resistance rated. 1.4. The grease duct system does not serve solid fuel-fired appliances.
2.Branch ducts from other equipment in the same kitchen area, or from registers exhausting the kitchen space in general, may be connected to the main hood exhaust duct if the following requirements are complied with: 2.1. A fusible link fire damper of the same gage as the hood exhaust duct shall be added at the point of connection of the branch duct to the exhaust duct. 2.2. If the branch connection is made to the portion of the ductwork that will contain the fire-extinguishing medium, then the fire dampers required in Exception 2.1 shall be arranged to close automatically upon the operation of the fire-extinguishing system. 2.3. The branch connection shall be made in either the top or sides of the main duct in a manner to prevent grease from flowing into the branch duct. 2.4. The branch ducts shall be constructed of steel, aluminum, or copper of the gages and weights required in Chapter 6, and they shall be insulated with 2 inches (50.8 mm) of magnesia or other material having equivalent insulative and fire resistance qualities. 2.5. All registers in these branches shall have fusible link actuated dampers. 2.6. Where branch ductwork is to be used to exhaust vapors from dishwashers, pot sinks, or other similar equipment of a commercial type from which moisture is emitted, copper or aluminum of the minimum gage and weights required in Chapter 6 shall be used. Such ductwork shall be installed so that condensate cannot leak from it. 2.7 Type I and Type II exhaust systems can be interconnected downstream of filters with a fire damper at the connection to the exhaust system.
