Air purifiers equipped with a HEPA filter are capable of capturing up to 99.97 percent of particles as small as 0.3 microns, making them highly effective at trapping dust, dust mites, and other particles that are too small to be seen with the naked eye. The CADR rating indicates the volume of air that is filtered by an air purifier in a given amount of time, and is divided into three categories: smoke, pollen, and dust. The most efficient way to filter air in a home is through the forced air heating system or central air conditioning system. Due to growing concerns about indoor air pollutants, air purifiers have become increasingly popular.
However, they can only eliminate allergens while they are airborne; they cannot remove larger allergens such as dust mites and pet hair that settle on furniture and carpets. Filtering air filters pass air through a filter where pollutants are sequestered, and then return clean air to the room. Multiple studies have shown that HEPA filters can reduce particulate matter by 50 percent or more. The EPA does not recommend using DIY air purifiers as a permanent solution for indoor air quality, as their performance is not guaranteed.
Some air purifiers come with particle counters that detect how polluted the air is and adjust the cleaning speed accordingly. Hybrid filters combine both filtering and trapping methods, while some also include activated carbon elements to combat odors. The best way to improve indoor air quality is to eliminate sources of pollutants and ventilate with fresh outdoor air. An extended media filter is like a stack of oven filters that are 8 inches thick.
If allergies prevent you from opening windows, use the air conditioner or forced air cooling system with a clean filter. HVAC systems in large buildings typically filter the air before it is distributed throughout the building, so consider upgrading HVAC filters as appropriate for your specific building and HVAC system (consult an HVAC professional). DIY air purifiers can provide some benefits for reducing concentrations of viruses and other indoor air pollutants, but research is limited and there are several important considerations to keep in mind.