The Dyson Purifier Cool Gen1 purifying fan automatically senses, captures and traps pollutants to purify your whole room, while removing 99.97% of particles as small as 0.3 microns. Tested per Dyson internal test standards for whole-room air projection (TM-005021) and purification coverage (TM-003711) Particle challenge by DEHS oil specified in EN1822 within a chamber specified in ASTM F3150. Tested in Max Mode for whole machine efficiency above 99.95%. Gas capture rate vary. Tested per ISO 29463.