If you are having problems with the air quality in your home, you might be shopping for an air purifier. But with so many different kinds of air purifiers on the market it can be hard to know if they are truly effective.
This uncertainty is not unfounded: class-action lawsuits have been brought against major brands for making deceptive marketing claims. These cases might make you doubtful that air purifiers are simply elaborate scams designed to remove more money from your bank account than particles from the air in your home.
But the simple truth is that the right air purifier can dramatically reduce the number of pollutants in the air, and even cut down on toxic airborne chemicals like benzene or formaldehyde.
How do air purifiers work: The basics
The technology behind air purifiers is actually quite basic—it is essentially a fan blowing air through a filter (which, in fact, is how many of the most effective air purifiers on the market work). But the technology can also go beyond this basic setup. Some air purifiers also use electric ions, carbon adsorption or photochemical reactions to remove or even destroy particles and gaseous toxins in the air.
It is also true that some types of air purifiers are not as effective as others. Nevertheless, studies have found that a good air purifier can effectively improve air quality and help with certain health problems, including asthma and allergies. This is why it is imperative that you purchase the right kind of purifier that will most effectively address your specific air quality issues. We will take a look at how air purifiers work to remove pollutants from the air and what scientific research says about their effectiveness.
Do air purifiers work: What the research shows
Research studies (Fisk, 2013) suggest that certain types of air purifiers can be effective, particularly when it comes to improving the indoor air quality and certain health indicators for people with asthma or allergies. A 2011 review of multiple studies has noted that, “Studies support multiple interventions, including air filtration, as methods to improve outcomes in the treatment of allergic respiratory diseases” [Sublett, 2011].
The study also found that whole house air filtration systems installed in a home’s HVAC system provide significant benefits if it uses a high-efficiency filter, while portable air purifiers can increase air quality in the room in which they operate. Studies have shown that purified air in the sleep zone “can have a positive effect on bronchial inflammation and quality of life in patients with perennial allergic asthma” [Pedroletti et al, 2009]. Researchers have also noted that in order to maximize these benefits, portable air purifiers should be used in the “sleep breathing zone”—or, in other words, close to your bedside, where you spend a high proportion of your time.
According to the EPA, “Using a portable air cleaner and/or upgrading the air filter in your furnace or central heating, ventilation, and air-conditioning (HVAC) system can help to improve indoor air quality. Portable air cleaners, also known as air purifiers or air sanitizers, are designed to filter the air in a single room or area.” Specific studies also found that room air purifiers reduced the particulate matter from tobacco smoke in the room [Batterman et al, 2005].
How different types of air purifiers work for different types of pollutants
Air purifiers employ a range of different filtration technologies to clean the air. Here is a rundown of how the main types work for various pollutants:
HEPA: The fabric that is used in true HEPA filters must meet a government specification to remove 99.97 percent of particles at 0.3 microns in size. HEPA filters are mechanical filters that remove particles from the air by blowing air through a dense fiber weave, which traps the particles. These filters collect pet allergens, dust, pollen, particulate pollutants in smoke and mold spores on its surface. However, HEPA filters are not able to remove gaseous toxins, including VOCs (volatile organic compounds) from the air and can potentially provide a nutrient-rich surface for pollutants like mold to multiply.
PECO: The Molekule air purifier contains proprietary Photo Electrochemical Oxidation (PECO) technology that destroys pollutants at the molecular level. During the PECO process, light shines on a filter surface and activates a catalytic reaction. Mold, allergens, VOCs and other pollutants are converted into harmless substances, such as carbon dioxide and water. PECO technology is different from traditional air purification because pollutants like mold, allergens and VOCs are broken down, thus eliminating the chance of them being released back into the air.
UV-C: These air purifiers expose air (and the pollutants in the air) to an ultraviolet light. Theoretically, this light could deactivate microbes such as bacteria and viruses. However, in practice, this process requires a longer exposure time and higher power UV light than off-the-shelf consumer air purifiers provide, so they are unlikely to be effective.
Ionic/Ionizer: An ionic air purifier imparts an electrical charge to particles that pass through it, causing them to either clump together and precipitate out of the air, or to be drawn to a charged collector plate. They do not remove gaseous compounds at all, and in fact studies have found them ineffective even with regard to particles. According to the multi-study review, “Ionic electrostatic room air cleaners provide little or no benefit compared with WHF [whole house filters] or HEPA PRACs [portable room air cleaners]” [Sublett, 2011]. Moreover, ionizers emit ozone, a respiratory irritant that can build to unsafe levels in an indoor space.
Ozone generator: While ozone can be used to neutralize some pollutants in the air, ozone is itself a toxin and should only be used for professional cleaning (while no one is present when it is being used, and with the area fully ventilated after use). Because of this dangerous byproduct, the EPA recommends against using any kind of ozone generator in your home.
How long does it take an air purifier to clean the air in a room?
This is a surprisingly complicated question. One way to approach it is to look at how long it takes for all the air in the room to pass through the purifier, thus “cycling” throughout the room—it all depends on the size and power of the fan that the purifier uses and how difficult it is for air to flow through the purifier. This can be summarized by an air purifier’s CADR rating, which is measured in cubic feet per minute (CFM).
However, the CADR rating is not really an accurate gauge of how well an air purifier performs. A purifier with a massive fan and low-efficiency filter can have a very high CFM output, but the air is not being cleaned very effectively. A smaller unit with a quality filter might take longer to cycle the room, but it does a more thorough job of removing pollutants from the air. In general, the larger the space you want to purify, the longer it will take any given air purifier to clean the air.
Do air purifiers work for allergies or asthma?
Studies, including those cited above, suggest that air purifiers can help reduce the overall amount of allergens in the air, including pet dander, pollen and mold spores, as well as other particulate pollutants that may trigger symptoms of asthma or allergies.
HEPA filters and other air purifiers designed to remove particles from the air are best for this type of use. Studies have shown that a HEPA air filter reduced the amount of a particular dog allergen in a room [Green et al, 1999], and that “there is sufficient evidence that air filtration does reduce indoor levels of ambient particulates that might trigger disease processes themselves” [Sublett et al, 2010].
However, these studies also found that an air purifier alone would not remove all allergens from the air and might require constant use over a long term (weeks or months) to be truly effective. For instance, cat allergens are everywhere an indoor cat goes. An air purifier will not remove these allergens from the floor, furniture or curtains, so thorough, regular cleaning should be combined with air purifier use.
Source control is also important. For instance, if you are allergic to cat dander, not allowing your cat into your bedroom while also running an air purifier in your bedroom while you sleep can help improve air quality and could make a difference for allergy symptoms and better sleep than running an air purifier with the cat in the room.
Most allergens, with the exception of a few types of mold spores, are relatively large particles. This means that any air purifier capable of removing particulate pollutants from the air is a good choice for dealing with allergies and asthma. HEPA filters and PECO air purifiers can help in these scenarios.
How well do air purifiers work on dust, VOCs and other pollutants?
As with the allergens described above, air purifiers can remove the following pollutants:
Dust: While an air purifier that traps or destroys particulate pollutants, such as a HEPA filter or a purifier that uses PECO technology can remove dust from the air, an air purifier will not make your house completely dust-free. There are too many sources of dust in the average house for a portable room air purifier to remove them all. A whole house filter on your HVAC system will help to some extent, but the only way to really reduce dust in your house is the old-fashioned way: cleaning, sweeping and vacuuming.
VOCs: Volatile organic compounds are chemicals, many of them toxic to humans, that are emitted by a variety of household objects and products. New carpets or furniture can outgas VOCs, while cleaners, solvents, paints and other materials can add VOCs to the air in your home. A HEPA filter will not remove VOCs, and so a carbon filter is often added to an air purifier, which is able to remove the chemical molecules out of the air through a process called adsorption [EPA]. During the adsorption process, gaseous pollutants stick to the filter surface. However, carbon filters can become saturated, as well as run the risk of the gases “unsticking” from the filter, so a PECO air purifier that destroys molecules instead of trapping them might be a better option.
Mold: Mold is a fungus that spreads by emitting spores. These spores are particulate pollutants. When they land on a moist surface, the spores can grow into more mold (and emit more spores). Like other particulate pollutants, mold can be removed by HEPA filters and air purifiers that destroy particles. In fact, HEPA filters can collect mold spores so effectively that under certain conditions, mold can grow on the filter media and eventually be emitted by the air purifier [Kim et al, 2014]. For this reason, HEPA filters must be changed regularly. UV-C air purifiers can also supposedly deactivate mold spores, but consumer UV-C purifiers are not always powerful enough to accomplish this.
Smoke: Whether it comes from tobacco, weed, a fireplace or nearby wildfires, smoke is a complex pollutant. It consists of both particles and VOCs, and both elements can be harmful. Air purifiers have been found to consistently remove the particulate portion of smoke from the air [Rice et al, 2018], but struggle to remove the VOCs. A carbon filter, or a dual-stage carbon/HEPA filter could work, but the filter media would require frequent replacement—a PECO air purifier that destroys VOCs may be a better option.
As part of a multi-step approach to air quality that includes source control and proper ventilation, research shows that a high-quality, efficient air purifier can remove particles and VOCs from the air and have a measurable effect on the air quality in your home. A portable room air purifier allows you to target the places where you spend the most time, especially the room where you sleep, which will maximize the benefits you get from your air purifier. To learn more about the Molekule air purifier, which goes beyond simple particle capture and destroys pollutants like mold, allergens and VOCs at the molecular level, see here.