A gas sensing system for an air conditioner unit is provided. The air conditioner unit includes a bulkhead that divides a cabinet into an indoor portion and an outdoor portion, and a compressor circulates refrigerant through a sealed system. An electrically protected housing is positioned within the indoor portion and defines a sensor enclosure for receiving a gas sensor for measuring a gas concentration of leaked refrigerant within the sensor enclosure. The housing includes vent apertures to permit leaked refrigerant to enter the sensor enclosure while the vent apertures are covered by filters to prevent contaminants from entering the sensor enclosure.