Abstract: A recessed detector assembly having the capability to detect and evacuate air laden with airborne substances from within the assembly. The assembly includes a detector frame adapted to be flush mounted into a mounting box mounted in a ceiling or a wall, the frame having exposed vents allowing air containing airborne substances to enter the frame; at least one sensor mounted in the detector frame for sensing one or more of the airborne substances; means for exhausting the airborne substances, the at least one sensor generating a signal causing an exhaust fan or a drop down sensor for evacuating the one or more airborne substances to operate when a presence of the one or more of the airborne substances is sensed to exceed predetermined levels. Accordingly, the detector may be promptly reset and an alarm may be promptly turned off when airborne substances in the room drop below the predetermined levels.