The Holmes True HEPA 360 Air Purifier features a 3-in-1 filter with 3 layers of filtration. The first layer serves as a pre-filter that caputures large particles such as pet hair and dust bunnies. The air then passes through the True HEPA filter capturing particles as small as 0.3 microns to remove up to 99.97% of airborne particles. Finally, the carbon-filter eliminates common household such as cooking fumes and pet odors. The optional ionizer helps to bind smaller particles to form larger particles that are more easily captured. The capacitive touch control panel lets you easily control the air purifier settings – from 3 speeds to 8 hour timer. The Holmes True HEPA 360 Air Purifier also features a Filter Reminder Light that alerts you when it's time to change the filter.