Abstract: A system and apparatus is provided for minimizing damage caused by leaks from a packaged terminal air conditioner (“PTAC”) or heat pump (“PTHP”). A shutoff switch can be operatively connected to the front desk circuit of a PTAC/PTHP. The switch is configured such that, when it is exposed to water, the PTAC/PTHP is automatically deactivated to prevent further leakage. The shutoff switch includes a plurality of spaced, non-insulated conductors enclosed between a non-conductive base layer and a water absorbent layer. The water absorbent layer is in contact with the conductors. Electrical connection between the conductors is permitted when the absorbent layer is sufficiently wetted, but there is no electrical connection between the conductors when the water absorbent layer is dry. The switch can be placed on or near the PTAC/PTHP, on the floor or wall beneath the PTAC/PTHP and/or on a wall sleeve that receives the PTAC/PTHP.