A smoke alarm with protection mechanism

The invention provides a smoke alarm (1) comprising a housing (2) delimiting a battery compartment (10); a fastening cover (3) adapted to be mounted to a support and to be connected with the housing (2); and protection mechanism for preventing installation of the smoke alarm (1) without a battery (11). Said protection mechanism comprises at least one spring member (17) having at least one side arm (17a,17b) and a lower arm (17c), which is connected with the at least one side arm (17a,17b) and located along and seated in the bottom (15) of the battery compartment (10). The lower arm (17c) is movable between the first position, when at least one battery (11) is missing in the battery compartment (10), in which the connection region of the lower arm (17c) and the at least one side arm (17a,17b) is located at distance from the bottom (15) and in which the at least one side arm (17a,17b) protrudes above the top surface of the housing (2) and prevents attachment of the housing (2) to the fastening cover (3) and the second position, when all batteries (11) are located in the battery compartment (10), in which the connection region of the lower arm (17c) and the at least one side arm (17a,17b) is located adjacent to the bottom (15) of the battery compartment (10) and in which the at least one side arm (17a,17b) is retracted below the top surface (6) of the housing (2) to allow attachment of the housing (2) to the fastening cover (3).