This protective cover has been helping stop false fire alarms around the world for more than 30 years, without restricting legitimate alarms. This Stopper II® enclosure with heater allows addressable dual monitor modules to be installed inside or outside in temperatures below UL Listing limits or in other NEMA 3R environments. UL/cUL Listing requires outdoor rated stations. The cover offers excellent protection against physical damage (both accidental and intentional), as well as other environments inside and outside. Also ideal for inside of walk-in freezers.