A device that purifies the air to remove impurities and pollutants is an attractive prospect, but how does an air purifier work?
In this function, we encountered an urgent question: how exactly does the air purifier work? Part of the reason is that due to the COVID-19 pandemic, we spend more time indoors and have more general concerns about the quality of the air we breathe.
A recent report by the U.S. Environmental Protection Agency showed that the content of pollutants such as mold, pesticides, and particulates in indoor air is five times that of outdoor air. Therefore, the idea of a device that can remove these pollutants and dust and other allergens, Pet dander and pollen seem to be not only practical, but also a healthy choice. But how do the best air purifiers work, what can they remove, and can they prevent COVID-19?
Air purifiers purify the air and remove pollutants, allergens and toxins; unlike air filters, air filters only remove them from the circulation. But how does an air purifier actually work?
The setup of an air purifier is relatively simple: a fan that sucks in air and one or more filters. These filters—usually fibers or nets such as paper and glass fibers—capture and neutralize pollutants and particles as the air passes through them, and then recirculate the clean air into the living space.
They can effectively filter out most polluting particles, although some may remain on hard and soft surfaces, such as furniture or walls. The specific airborne particles emitted from the air depend on the type of air purifier and filter used.
Most filters will capture relatively large coarse molecules that are 5 microns or less in size, such as dust mites and pollen. But how does an air purifier filter out smaller particles? The high-efficiency filter uses a dense fiber network and several layers of complex weaves to remove pollutants and allergens as small as 2.5 microns, about the size of animal dander. Some air purifiers have ultraviolet filters and use light to destroy biological impurities such as mold and bacteria, while those with activated carbon can remove gases such as volatile organic compounds (VOC) and smoke particles. Therefore, an air purifier can help alleviate allergies to a certain extent.
In the early days of the pandemic, as a large number of shoppers went online looking for air purifiers, many manufacturers hinted that their machines could withstand COVID-19.
The size of COVID-19 particles is about 0.1 micron—1,000 times smaller than a millimeter and thinner than a strand of spider web filament—but they are always combined with something larger, such as water droplets or aerosols. Just like other airborne viruses and bacteria, these droplets can be removed by air purifiers.
Therefore, the new type of coronavirus that causes COVID-19 should be filtered out using HEPA air purifiers. In this way, this air purifier can help reduce the spread of the virus. However, whether this means that these purifiers can prevent direct transmission-such as an infected person sneezing or exhaling virus particles a few feet away from you-is unclear. The air purifier needs time to capture these particles, and when the air is sucked into the purifier, it may have entered your nose.
Aneta Ivanova, an allergy nurse consultant at the Midlands Allergy Service Center in the United Kingdom, told Live Science: “We are still in the beginning stages of research on how to manage and protect the population from COVID-19 and its many variants.” “The COVID particles do indeed. The high-efficiency particulate air (HEPA) filter in some air purifiers can capture the particle size range, that is, 0.01 µM/micron or larger. Placing the air purifier next to it may improve the environment for a sick patient, but Will not protect yourself from COVID."
A 2021 report from the Centers for Disease Control and Prevention (CDC) suggests that this may be true. Their carefully controlled research shows that HEPA air purifiers use mechanical suction to suck air into high-efficiency filters, which can reduce indoor (such as meeting rooms) exposure to COVID-19 aerosols. However, the researchers did not consider factors such as open windows, room size, and airflow-all of which affect how the air purifier operates under real-world conditions. We conducted a separate investigation on whether the HEPA filter removes viruses.
NASA satellite data shows that climate change is related to an increase in the average number of wildfires worldwide, especially in the United States. These fires produce large amounts of smoke-a complex mixture of fine particles, about 30 times smaller than the diameter of a human hair, and gases such as carbon monoxide, nitrogen oxides, and volatile organic compounds.
These particles and gases may harm human health, so it is recommended that nearby residents stay indoors in the air filled with wildfire smoke and close doors and windows. But what about the particles that have entered the living space? How does an air purifier solve these problems?
A study published in the journal Environmental Health in 2016 showed that air purifiers or portable air purifiers should be at the forefront of public health response measures to prevent exposure to indoor wildfire smoke. How can air purifiers reduce particulate matter from wildfires? The study recommends equipment equipped with HEPA filters to eliminate particles and pungent odors. It also pointed out that air purifiers with electrostatic precipitators—using electrical energy to charge incoming particle streams and collecting them on oppositely charged metal plates—can reduce the concentration of fine particles.
But what if you can't get the air purifier? Can I do it myself? Actually, yes; all you need is a box fan and a HEPA or high-quality filter. You can make two types of air purifiers: the first one uses a fan and a filter, while the second one has a slightly more complicated structure and uses a double filter placed above the fan.
These self-made air purifiers work in the same way as the manufacturing equipment and are quite effective. Both the New York Times and the Los Angeles Times have produced and tested their own versions. Research by the Agency for Science, Technology and Research of Singapore (A*STAR) considered different filter materials for their DIY air purifiers, including HEPA filters, surgical masks and melt blown polypropylene. They found that each material was about 80% efficient in filtering particles and aerosols.
However, box fans are not designed for this purpose. Their motors must work harder to draw air into the filter. Therefore, these homemade air purifiers increase the risk of fire and should be used with caution.
So, how does an air purifier work? By capturing most pollutants and allergens, some will always remain in the air. Therefore, it is best not to use an air purifier alone, but to complement other strategies to improve air quality, such as increasing cleaning or using environmentally friendly cleaning products to reduce irritants, using indoor plants to help improve air quality and improving home ventilation.
Kerry is a freelance writer and editor who specializes in topics related to science and health. Her work has appeared in many scientific and medical journals and websites, including Forward, Patient, NetDoctor, YourWeather, AZO Portfolio and NS Media.
Kerry's articles cover a wide range of topics, including astronomy, nanotechnology, physics, medical devices, pharmaceuticals, and mental health, but she is particularly interested in environmental science, clean technology, and climate change.
Kerry is trained by the NCTJ and holds a degree in natural sciences from the University of Bath, where she researched a range of topics including chemistry, biology, and environmental science.
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