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.
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. 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.
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 an industry 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. Over time a HEPA filter may become less effective as it fills with pollutants.
Carbon: Almost all purifiers contain some carbon, also known as charcoal or activated carbon. Carbon is the oldest purification method and is easily made from charred wood or pulp. Tiny binding sites on the surface can chemically attract pollutants like VOCs, nitrogen oxides, and other pollutants. Like HEPA, carbon has a limited number of places where pollutants can be trapped and loses effectiveness over time.
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 that are broken down can’t be released into the air again. PECO filters still have to be replaced on time because even though the catalyst destroys organic pollutants, very small inorganic pollutants in the air like bits of rock and sand can build up and prevent the catalyst from being activated by the light.
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. Any device that uses UV-C to kill pathogens has to be designed such that the contaminated airstream spends enough time irradiated by the light or they may remain viable.
Ionic/Ionizer: An ionic air purifier imparts an electrical charge to particles that pass through it, causing them to either clump together and fall 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 can 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.
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 carbon filter is often added to a HEPA air purifier to improve effectiveness against VOCs. A carbon filter is able to remove the chemical molecules out of the air through a process called adsorption [EPA]. However, remember that carbon filters can become saturated, as well as run the risk of the gases “unsticking” from the filter.
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.
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, or a PECO air purifier that destroys VOCs.
As part of a multi-step approach to air quality that includes source control and prope r 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.