A method for fire detection in enclosed environments (1) subject to explosion protection regulations out of which an air-dust mixture is filtered while the concentration of dust of the air-dust mixture is lowered to under the explosion limit by a filter (2) and the aspirated air-dust mixture is checked for burning characteristics and if appropriate a fire alarm is triggered, in which the function of the filter (2) is monitored, the fire detection is carried out by use of an aspirating smoke detector system (7) not approved for use in potentially explosive areas but instead is deployed outside the ex-zone and if the filter (2) is destroyed a signal processing unit (15, 15.1) of a malfunction monitoring sensor (14) generates a signal which initiates a subsequent action preventing aspirated air-dust mixture with an elevated concentration of dust from entering the aspirating smoke detector system (7).