Abstract: A smoke detector with an input port belonging to an existing light fixture, the input port connected to a housing and electrically to an AC to DC converter. The housing accommodates a communication module such as Bluetooth and/or WIFI operable to act as a node, a microprocessor, and a smoke detecting unit. When the smoke detecting unit detects hazardous smoke emitted from environment over a threshold, it can wirelessly issue alarm and notify the persons nearby and people in charge.