In a pre-action system the piping is pressurized with air or nitrogen, monitoring of this air pressure provides a means of supervising the system piping. Loss of the supervisory air pressure in the system piping results in a trouble signal at the alarm panel. A fire alarm of a possible fire allows time for alternate fire extinguishment prior to a sprinkler discharge. In the event the fire cannot otherwise be extinguished, the precaution sprinkler system will then perform as the primary fire protection system. They are designed for applications such as refrigerated areas that require maximum protection against inadvertent operation of the sprinkler system.