Abstract: A portable industrial toilet cabin is provided with a smoke-sensitive alarm unit for detecting smoking by an occupant of the toilet and emitting an alarm signal responsive thereto. The unit is useful, for example, in industrial and like areas where smoking is a hazard and is therefore prohibited. The unit may be mounted around a purpose-formed opening in an inclined roof of the cabin by a specialized adapter that mounts the unit in a horizontal disposition, and which may include a security screen for preventing occupants of the toilet from tampering with the alarm unit.