Abstract: In order to allow a smoke detector unit to be utilized in, for example, a domestic kitchen environment, appliances whose operation is commonly associated with the generation of non-hazardous smoke or aerosols are connected to a conventional mains supply socket via a current monitoring unit. The current monitoring units include a radio transceiver, which transmits the operational status of the appliances to a corresponding transceiver of the smoke detector unit 1. If the signals transmitted by the current monitoring units indicate that the appliances and are off, the smoke detector unit generates a warning signal when the smoke density exceeds a lower threshold. If one of the appliances and is detected to be on, the smoke detector unit generates a warning signal only when a second, higher threshold of smoke density is exceeded. Optionally, when the higher smoke density threshold is exceeded; the smoke detector unit transmits the signal to the current monitoring unit to power off the appliances.