The DEF ceiling swirl diffuser proves suitable for use in offices, hospitals and shops. The device can be easily installed in false ceiling or can be freely hinged at height of between 2.6 and 4.0 m above the floor. The DEF diffuser enables changing of the air distribution by adjusting the deflectors. The air flow ranges between 70 and 300 l/s (245/1070 m3/h). The device can be used with minimum air temperature distribution within 10°C lower than that of the environment.