A separate grease duct system shall be provided for each Type I hood. A separate grease duct system is not required where all of the following conditions are met:
- All interconnected hoods are located within the same story.
- All interconnected hoods are located within the same room or in adjoining rooms.
- Interconnecting ducts do not penetrate assemblies required to be fire-resistance rated.
- The grease duct system does not serve solid-fuel-fired appliances.