What Does an Air Purifier Do?

What does an air purifier do? An air purifier improves your indoor air quality by removing air pollutants from your home with filters or other technology. Knowing how each type of air purifier works will let you choose the best air purifier for you.

There are many different types of air purifiers, and each one works using different technology. Whether it’s a HEPA filter, carbon filter, ionizer, or PECO purifier such as Molekule, each air purifier is effective against different types of pollutants. The right air purifier for your family will depend on the types of pollutants in your home. 

Types of Air Purifiers and How They Work

  • Mechanical filters – A mechanical filter removes particulate pollutants from the air by passing air (propelled by a fan) through a filter made of paper, fabric, or fiberglass. The filter is a tangled mesh that catches the particles letting clean air out the other side. A HEPA filter is a filter made to meet a specific standard — trapping 99.97 percent of all particles that are 0.3 microns in size or more. According to this review of air purifier technology in the Journal of Allergy and Clinical Immunology, mechanical filters become more effective as they trap more particles, but eventually become clogged and require replacement. This can be inconvenient and expensive.
  • Carbon filters – Carbon filters pass air over or through activated charcoal or another form of carbon. The carbon captures molecules of many chemical gasses, including volatile organic compounds (VOCs), a common air pollutant. It’s able to do this because carbon has many open spots where the molecules can become attached, a process known as adsorption. Charcoal is often used for carbon filtration because it’s relatively inexpensive and has an enormous surface area which allows it to capture many organic molecules. Carbon is good at removing ozone from the air, but carbon filters can lose their efficiency because all of the molecular attachment sites get “filled up.” The filter will then need to be replaced. Particulate pollutants are not removed by carbon filters. They only remove gaseous pollutants.
  • Ionizers – Ionizing air purifiers use an electric current to give particulate pollutants an electrical charge. The charged particles are then attracted to things with the opposite charge, which could be other particles (causing them to clump together and settle out of the air) or nearby surfaces like rugs, furniture, or curtains. Some ionizers have a charged plate that attracts the particles, which needs to be cleaned frequently. Ionizers do not remove VOCs from the air. The biggest drawback of ionizing air purifiers is that the electric current generates ozone as a side effect. 
  • Ozone Generators – While ionizers create ozone as a side effect, ozone generators create it intentionally. Ozone can build to unsafe levels in an enclosed space. The Environmental Protection Agency (EPA) calls ozone a lung irritant and recommends against using ozone generators.
  • PECO – PECO stands for photoelectrochemical oxidation. This technology purifies air by creating a chemical reaction activated by light. The reaction destroys organic materials, including VOCs, mold spores, bacteria, and viruses by oxidizing them. PECO air purifiers don’t generate ozone — in fact, they are effective at removing ozone from the air.

Indoor Air Pollution Sources

Knowing what types of indoor air pollutants are in your home and where they come from will help you develop an effective strategy for removing them.  This often means using an air purifier. 

  • Particulate pollutants – These pollutants are solid particles light enough to float in the air, ranging in size from easily visible (ash, pet hair, pollen) to microscopic (mold spores, dust mite feces, pet dander). They can come from a variety of sources in the home, including pets, fireplaces, cooking, smoking, and even the people living in the house — your skin and clothing all shed tiny particles that accumulate over time. Particles can also be introduced from outside the home, such as dirt carried in through an open door or pollen coming in through an open window. A mechanical filter such as a HEPA filter is an effective way to remove particulate pollutants from the air.
  • VOCs – VOCs are gaseous pollutants that can be toxic. There are many potential sources of VOCs inside your home, including paints, wood preservatives, cleaners, aerosol sprays, and petroleum products or pesticides. Plastics, including many modern fabrics, can also give off VOCs by a process known as offgassing. According to the EPA, levels of VOCs inside homes can be 2 to 5 times greater than outside air. Opening windows to let in fresh air can reduce VOC levels. A carbon air purifier or a PECO air purifier that can destroy VOCs would further reduce VOC levels and also be effective when the windows can’t be opened.
  • Mold – Mold is a fungus that gives off spores. The spores can be a respiratory irritant, causing allergy symptoms or asthma attacks. The key to reducing mold spores in your air is source control — mold requires moisture to grow and release new spores. Identify the source of the moisture and remove it. Fix leaks and broken pipes. If mold is caused by excess humidity, increase ventilation or use a dehumidifier with a humidity sensor. Clean up all mold, throwing away any porous items such as carpets, drywall, or wood that has been covered in mold. A good particle filter will remove mold spores from the air. A PECO air purifier destroys mold spores completely, preventing them from colonizing the filter media and releasing more spores.
  • Carbon monoxide – Carbon monoxide (CO) is a very serious pollutant that can build to unsafe levels any time combustion occurs indoors without being properly vented. Sources include gas stoves, kerosene heaters, gas furnaces, fireplaces, and automobile exhaust. Carbon monoxide is invisible and odorless and can quickly impair and even kill anyone exposed to high concentrations. No air purifiers are designed to remove carbon monoxide. It’s vital to use carbon monoxide detectors in your home. If you suspect a carbon monoxide buildup, open the windows and get out of the house, then call the fire department.
  • Allergens – Although allergens are particulate pollutants, it’s helpful to look at them separately and understand where they come from and how to reduce them
    • Pet allergens come from our pets’ fur and skin. They can be reduced by changing how often you bathe your pet. Talk to your veterinarian, as some pets may benefit from more baths, while others may produce more allergens if they are bathed too often. You can also limit what rooms your pet has access to. 
    • Dust mites are microscopic bugs related to ticks that feed off of the organic materials in dust. Their secretions and feces are allergens. Regular vacuuming, using a vacuum with a HEPA filter, can reduce dust and dust mites. According to the University of Rochester, using dust-proof covers on mattresses, box springs, and pillows can reduce exposure to dust mites. Running a dehumidifier can also help since dust mites prefer warm, moist air.
    • Pollen is produced by plants at certain times of the year, which can be different depending on what part of the country you live in. While opening windows is typically a good way to improve indoor air quality, during pollen season you’ll want to keep the windows closed and turn on the air-conditioning. A mechanical filter such as a HEPA filter, or an air purifier using PECO technology, can remove pollen and other allergens from the air.

This close look at different types of air purifiers and indoor air pollutants should answer your questions about what an air purifier does, and help you make an informed decision about what air purifier will do the best job in your home.