Are air compressors required to be UL Listed or FM Approved?
No, compressors are not required to be listed/approved. They only need to have enough capacity (hp) to replace the operating air pressure in dry-pipe and double interlock preaction systems within 30 minutes. However, the device used to automatically regulate the air pressure in a sprinkler system must be listed/approved. Hence, a pressure maintenance device must be used. The pressure switch on an automatic air compressor does not qualify as an appropriate means of automatically regulating air pressure in sprinkler system piping.
