When properly maintained and sized, air purifiers can improve the quality of air. Choose a model that has true High Efficiency Particulate Air (HEPA) filters, so the cleanest air possible is sent back into the room. Activated carbon filters are also a good option. Both are effective at trapping airborne chemicals, odors, pollen, dust, bacteria and more. Change the filters according to manufacturer’s guidelines. Be sure to buy an air filter that is sized for the room. For example, an air filter for a 100 square foot room will not be big enough for a 500 square foot room.
The best models have filters that trap particles in the air that are at least as small as 2.5 micrometers (i.e. PM2.5). These particles can include organic compounds, motor vehicle exhaust, cigarette smoke, and some industrial processes.
A low cost alternative to buying a commercial air filter is to make a box fan filter. These have been found to reduce particles in the air quite a lot.The University of Washington has a guide on how to make one from a box fan, a MERV 13 furnace filter, and some duct tape or bungee cords.
Clean and/or change the air filter on your heating and/or air conditioner system once a month. The filter traps pollutants, including dust, dirt, and microscopic particles. You should also check the filters in your clothes dryer and vacuum cleaner. All of these items have filters that need cleaning or replacing on a regular basis.