Abstract: A device and method for controlling fuel-air ratio during combustion of ground in a coal power plant, including pneumatic delivery of ground coal to the burners and feeding combustion air to burners while controlling the combustion air and the amount of carrier air. A high reliability of control combined with low maintenance of the air mass measurement devices is achieved. This is achieved by a measurement device for measuring the amount of combustion air which, according to correlation measurement, evaluates the triboelectric effects on sensors. Between 0.1 mg and 10 mg of fine-grained particles of a diameter between 20 ?m and 200 ?m are introduced per m3 air into suctioned fresh air, which is carried out during the starting of the firing system. This is done by correlation measurement that evaluates triboelectric effects on sensors, arranged in series in carrier air stream in direction of flow of the carrier air.