The optional Smoke Detector (MBS-SD) can alert the user to smoke within their growing area at ALL TIMES. Up to 5 smoke detectors can be connected to a single Hydro-x controller. If ANY of the smoke detectors determine there is smoke in the area, the user will receive a user-alert on their phone to alert them to the potential problem BEFORE the problem gets out of hand. "Sensors should remain dry and clean to prevent premature failure. Do not spray foreign substances or allow water / condensate on the sensors"