A 5-story parking garage has a noncombustible ventilation shaft that is accessible through a door at the lowest level. The top of the shaft is covered by an open grate. The requirements of NFPA 13 2019 edition (Section 9.3.3) call for a sprinkler at the top and bottom of the shaft. I would like to omit one or both, but can't find a good code justification.
The sprinkler at the top will be extremely difficult to install/service, and has nothing above it to collect heat. The one at the bottom seems more appropriate in case of trash accumulation, but will need to have an aux. drain since it is served by a dry system. We all know that drum drips in remote locations behind locked doors tend to have a higher likelihood of freeze ups.
This scenario doesn't seem much different than a large piece of mechanical equipment that has an access point for service and is not intended for occupancy. It's simple for me to just design it with the heads, just curious if anyone had good arguments for or against omitting them.
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