Air purifiers have become an increasingly popular way to improve indoor air quality in homes and offices. But how exactly do air purifiers work to clean the air? This comprehensive guide provides an overview of air purifier technologies, considerations when selecting an air purifier, and tips to get the most out of your device.

How Air Purifiers Work

The key components of an air purifier are the fan and the filter(s). The fan draws air into the purifier, then passes it through one or more filters to capture pollutants before circulating the cleaned air back into the room. Air purifiers use different filtration methods to remove contaminants from the air:

Mechanical Filters

Most air purifiers use mechanical filters made of densely woven fibers or finely meshed screens to physically trap particles as air flows through. Common types include:

  • HEPA filters: High efficiency particulate air (HEPA) filters can capture over 99.97% of particles above 0.3 microns in size using a very dense fiber matrix. This includes most pollens, mold spores, bacteria, and dust.
  • Activated carbon filters: Activated carbon adsorbs gases, odors, and chemicals rather than trapping particles. The porous carbon surface attracts and binds contaminants to remove them from the passing airflow.
  • Pre-filters: Less dense woven filters designed to capture larger particles first to prevent early clogging of the finer main filter. Pre-filters can be cleaned or replaced more frequently.

Electronic Air Cleaners

Some air purifiers use electronic attraction and oxidation rather than physical sieving to remove contaminants:

  • Electrostatic precipitators: Particles get electrically charged then captured on oppositely charged plates.
  • Ionizers: Negatively charged ions attach to particles to make them easier to filter. Can produce trace amounts of ozone.
  • UV light: Germicidal UV light destroys biological pollutants like bacteria and mold spores as they pass by the UV bulb.
  • Photocatalytic oxidation (PCO): Uses UV light with a titanium dioxide coated filter. The TiO2 catalyzes chemical reactions to break down gases and odors into safer compounds.

Choosing an Air Purifier

With many different air purifier models available, it helps to consider a few key factors to find the right one for your needs:

Room Size

Air purifiers work best when matched to the size of the room based on the unit’s clean air delivery rate (CADR). The CADR indicates the cubic feet per minute (CFM) of filtered air delivered for a given particle size or type of contaminant.

Look for a CADR at least 2/3rds the room size for adequate air cleaning. For example, a 200 CFM CADR rating would suit a 300 square foot room.

Filtration Type

True HEPA filters reliably remove over 99% of particles 0.3 microns and larger. This includes most allergens like dust, pet dander, pollen and smoke. Activated carbon also helps filter gases, VOCs and odors.

Avoid ozone generating ionizers or “electronic air cleaners” as they can produce harmful byproducts.

Special Features

Added Features like air quality sensors, timers, multiple fan speeds, and remote controls allow for automation and customization but increase costs. Focus first on the filtration performance needed.

Noise Level

Check decibel ratings (dB). Under 50dB is considered quiet. Levels over 60dB can disturb sleep or conversations.

Energy Use

Look for Energy Star rated models to save on electric costs from frequent, long-term operation. Check the wattage rating.

Using Your Air Purifier Effectively

To improve indoor air quality, air purifiers work best as part of a comprehensive strategy:

  • Control sources of pollutants by not smoking indoors, using non-toxic cleaners, and keeping humidity below 60% to discourage pests and mold growth.
  • Ventilate regularly by opening windows or adjusting HVAC systems to bring in fresh outdoor air. Stale indoor air can contain higher contaminant levels than outdoor air.
  • Then use air purifiers to filter recirculated indoor air. Portable room air cleaners are less effective than whole home systems, but provide benefits in individual rooms.

For optimal performance:

  • Replace filters regularly as indicated by the manufacturer, typically every 6 to 12 months depending on use. Effectiveness drops as filters fill with trapped particles.
  • Choose a central room location for air flow, away from walls and furniture. Place near known pollutant sources like litter boxes or craft tables if possible.
  • Close doors and windows so the unit filters a higher proportion of the room air.
  • Run the unit continuously at the highest tolerable fan speed to filter more air per hour. High speeds increase noise but maximize air cleaning.

While no single air purifier eliminates all indoor pollutants, using the right unit properly can effectively reduce contaminant levels and improve home air quality. Coupled with other good household habits, portable air cleaners provide healthy air benefits to enhance respiratory wellness.


What types of air pollutants do air purifiers remove?

Air purifiers can effectively remove various types of pollutants, including airborne particles such as dust, pollen, pet dander, and mold spores. They can also eliminate odors from smoke or cooking, as well as certain volatile gases and chemicals like formaldehyde.

Do air purifiers emit ozone that could be harmful to health?

Some older models of air purifiers use ionization technology that emits ozone as a byproduct. However, most modern air purifiers use different methods such as HEPA filters or activated carbon to clean the air without producing any ozone at all.

Can an air purifier completely rid my home of indoor pollution?

While an air purifier is effective in reducing levels of airborne pollutants in your indoor environment, it may not completely eliminate them all. The effectiveness depends on the type and size of the unit you choose for your specific needs and room size. It’s important to consider other factors too, like proper ventilation and cleaning habits inside your home, which can help support better indoor air quality overall. For more information, check out our guide on the benefits of desktop air purifiers.


Hey there, I'm Kevin, editor of Xievo. I'm passionate about air purifiers and providing accurate information to help readers make informed decisions. In my free time, I love hiking and experimenting with air purifiers in my own home. Thanks for visiting Xievo!