For a number of years it has been a problem to keep rats and mice away from rooms where food and the like are stored which attract said rodents. The problem is particularly pronounced when gate- and doors to said rooms are open for periods during loading and unloading of goods, and especially during periods of darkness. The invention relates to a method of chasing rats and mice from defined are- as, as well as gates and / or door openings in the wall of a building, characterized in that an air flow is generated at a fan unit (12) when gate- and / or door openings (2) open, which airflow through pipelines (14, 16, 18) is directed to nozzle openings (22) at least in a dispenser (6) arranged at or near terrain level, which spreads the air flow in the direction away from the areas, or away from the gate- and/or the door openings (2), along the wall (26) near said openings (2), and the area (32) in front of said openings (2) in a direction away from the openings. Rats and mice will instinctively away from the airflows and thus away from the gate and / or door openings (2). The invention further comprises a device for practicing the method, which may also be provided with one of the airflow generated by the blower unit (2), powered ultrasonic flute unit (40) which emits sound within the frequency range 20-30 KHz, and an odor dispenser which emits odors scaring rats and mice.