A duct detector housing includes a housing cover and a housing body defining a midline between the center of a detector and a printed circuit board within said body. Gas inlet and outlets are off axis of the midline to allow water that collects in conventional housing to drain from the housing. A maintenance mode button associated with a duct detector housing cover that is secured to a housing body of the housing provides a preselected time period during which removal of the cover is independent of a cover removal alarm. A printed circuit board within the housing has dedicated terminal blocks providing grouped connections with each of the groups segregated from another. An improved duct detector terminal has a hole in the terminal adapted to receive a test meter probe therethrough to provide an electrical contact between the wire.