What is an incidental use?
This type of use falls into the category of a mixed-used scenario. However, it is not addressed in the same way that other mixed uses are addressed. There are times where the hazards associated with a particular use do not rise to the level of requiring a different occupancy. The hazards must still be addressed because of the nature of the hazard and its impact on the remainder of the building.
These types of uses are regulated independently of the other mixed-occupancy provisions. They are one or more rooms or areas in a building that pose risks not typically addressed by the provisions for the general occupancy under which the building is classified. These areas are never intended to be considered different occupancies, which would create a mixed-use scenario.
Examples of incidental uses.
Table 509.1 of the 2021 International Building Code provides a comprehensive list of these incidental uses. Most of the rooms or areas identified in the table are regulated where located in any of the occupancy groups, established by the code. A few of the areas only apply to specific occupancies or where certain volumes of certain items exist, or when an area exceeds an established square footage threshold. One thing that should be noticed about these areas is that most of these incidental uses will be unoccupied for extended periods of time. This creates a situation where a fire could grow unnoticed in addition to potentially high fuel loads or hazardous materials being present. Some of these areas include refrigerator machinery rooms, incinerator rooms and hydrogen fuel gas rooms not classified as Group H. The entirety of Table 509.1 has been provided below.
How are incidental uses protected?
Incidental uses are uniquely addressed using fire-resistance-rated separations or automatic sprinkler systems. or both. These fire resistance-rated separations are to be fire barriers and/or horizontal assemblies, typically having a rating of one hour. Where an automatic sprinkler system is required to provide the necessary protection, it need only be installed within the use under consideration. However, it is always highly recommended to protect the entire building. This will provide a much higher level of protection for all the occupants present, as well as significantly limit property damage during a fire event.
Automatic sprinkler systems are the best way to protect these incidental uses. Due to high fuel loads, equipment and hazardous materials present, the health and welfare of the building occupants should not rely on passive systems alone. Only sprinkler systems provide the necessary level of protection for these incidental uses.