An air purifier is a device that filters particles and irritants in the air and circulates purified air back into the room. Studies have produced encouraging results on the effectiveness of air filters in boosting indoor air quality.
People with asthma can take advantage of air purifiers to reduce their symptoms and frequency of asthma attacks. But with so many devices on the market, how do you choose an effective air purifier for asthma?
The Asthma and Allergy Foundation of America (AAFA)¹ estimates that over 25 million Americans have asthma, including over five million children. People with asthma commonly experience the following symptoms:
With certain triggers, asthma symptoms may drastically worsen, termed asthma attacks. These attacks are triggered mainly by allergens and other irritants. Allergens are small, fine particles in the air that are naturally harmless but can cause an allergic reaction in some people.
Air purifiers are purported to remove indoor irritants and contaminants - such as bacteria, viruses, allergens, dust, and mold - from the air to produce and circulate cleaner air. Still, many people remain skeptical about an air purifier's ability to ease asthma symptoms.
If you're considering investing in an air purifier, keep reading for details on how air purifiers work, the various types, and how to select the best air purifier for asthma.
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An air purification device features at least one air filter and a fan. As air enters the purifier, the filter captures the fine particles and irritants, including smoke, dust, pollen, mold, and others. The purifier then releases cleaner, purified air back into the room.
It's worth noting that air purifiers can only eliminate specific liquid and solid particles from the air, not gaseous substances, such as radon.
There are several types of air purifiers. One of the most popular mechanisms for air cleaners is the high-efficiency particulate air (HEPA) filter.
According to the US Environmental Protection Agency (EPA),² HEPA filters can theoretically rid the air of at least 99.97% of allergens and contaminants with a size of 0.3 microns (a micron is a very small unit of measurement equal to a micrometer, that is 10 meters). The efficiency rating is even higher for larger particles.
Other types of air purifiers include:
Electrostatic filters: These low-maintenance air filters use a low static charge or corona discharge wire to charge air particles passing through the device, collecting them on the oppositely charged plates.
Ultraviolet (UV) light filters: These filters use UV light to kill or inactivate airborne microbes, such as bacteria and viruses.
Ionizers: Also known as ion generators, ionizers use a high-voltage wire or fiber brush to electronically charge air particles that attach to particles in the air. The charged particles collect on the negatively charged plates or adhere to other surfaces in the room. However, ionizers can be harmful to health as they can generate ozone, which is a lung irritant.
A person may experience an asthma attack due to a high concentration of harmful particles in the air. When inhaled, these contaminants clog, inflame, and tighten the airways, triggering asthma symptoms. Air purifiers have been touted to be highly effective in cleaning indoor air. But how effective are they in reducing asthma symptoms?
In their review of relevant literature,³ one team of researchers found that air filters may increase peak expiratory flow rate (PEFR) in people with asthma. Doctors use PEFR to measure air coming out of the lungs, and it’s most commonly used in people with asthma. A higher rate indicates better airflow.
The researchers found a decline in indoor particulate matter (linked to respiratory and allergic diseases) associated with air purifier use.
While the majority of included studies failed to demonstrate a significant impact on respiratory symptoms and forced expiratory volume in one second (a measure of how much air someone can exhale during a forced breath), the evidence of the effects of air purifiers on indoor particulate matter and PEFR indicates the devices may be helpful for people struggling with asthma.
If you're in the market for an air purifier for asthma, pay attention to the following details:
The filter plays an integral role in an air purifier's efficiency, so look for a purifier with a high-efficiency filter. For instance, HEPA purifiers are demonstrated to remove at least 99.97% of harmful airborne particles with a diameter of 0.3 microns. It means that of every 10,000 particles that size, only three evade the filter.
It's also critical to check the minimum efficiency reporting value (MERV) rating. The MERV rating measures the ability of the device to capture particles with diameters of 0.3 to 10 microns. You should choose an air purifier with a MERV rating of 13 or higher.
The Allergy Standards Limited (ASL) and the Asthma and Allergy Foundation of America (AAFA)⁴ have joined forces to certify certain household products, including air purifiers. Usually, certified devices feature allergy-friendly filters with high efficiency.
Additionally, AAFA-certified air filters don't release ozone or reintroduce harmful particles into the air. While shopping for an air purifier, check the box for the “asthma & allergy friendly®” mark.
A good air purifier has a high air delivery rate to ensure the constant circulation of clean indoor air. Therefore, the device you choose should be appropriate for the size of the room you intend to use it in. The Environmental Working Group (EWG)⁵ recommends a device with a filter that replaces the air in an enclosure two or three times per hour, depending on the room's square footage.
Some air cleaners are loud, and it's best to avoid them. People with asthma often have sleep difficulties, and a noisy air purifier only worsens the situation. Find a device that operates at a low volume to ensure you have a comfortable sleep. You’ll be less inclined to use an air purifier if it’s disruptive.
Most ion generators release ozone, which can cause respiratory issues in people with asthma. Ozone causes the muscles of the airways to constrict and trap air inside the alveoli (small air sacs in the tubes of the lungs). The constriction leads to shortness of breath, wheezing, vulnerability to lung infections, and inflammation of the airways.
The EPA determined that ozone does not eliminate air particles. That's why many professional associations recommend HEPA filters instead of ionizers.
The Food and Drug Administration (FDA) hasn't approved any air purifier for the medical treatment of asthma. However, several studies have shown promising results in assessing air filters to reduce airborne irritants and contaminants. Some potential benefits of using an air purifier for asthma include:
If air purifiers can reduce reliance on anti-asthmatic medications, as demonstrated in the study detailed above, they can help alleviate the medical burden, which is measured by financial cost, morbidity, losses associated with the condition, and other factors affected by disease severity.
Cotinine,⁶ which forms after nicotine enters the body, is a common marker for environmental tobacco smoke exposure. In a 2017 study, a team of researchers from the Johns Hopkins School of Medicine and the Baltimore City Department of Health concluded that air purifiers could reduce cotinine levels in the saliva of non-smoking individuals.
Because cotinine is linked⁷ to hospital admission for asthma, air purifiers can help reduce asthma attacks and hospitalization.
Years into the COVID-19 pandemic, reducing the spread is still a hot topic. HEPA filtration effectively removes virus particles from the air, minimizing the risk of transmission. Recent data⁸ published by the CDC indicates that proper use of HEPA air cleaners reduces exposure by up to 65% without and up to 90% with universal masking.
Indoor allergens can trigger asthma attacks, hay fever, and other types of allergies. Coughing, wheezing, congestion, and sore throat are asthma symptoms that disrupt your daily functioning and sleeping habits.
Inadequate sleep causes many problems, including daytime drowsiness, affecting productivity levels. An air purifier can alleviate symptoms to improve your quality of life and sleep. However, keep in mind that maintenance is crucial, as a poorly maintained or contaminated purification system can actually make symptoms worse.
Few things are as refreshing as taking a deep breath of clean air. Unfortunately, asthma symptoms can make breathing difficult. Investing in an efficient air purifier for asthma, ideally one with a HEPA filter can significantly reduce airborne particles that can trigger asthma attacks.
If you’re in the market, choose an air purifier with a MERV rating of 13 or above that’s capable of circulating the air within a room two or three times hourly. Beware of terms that may indicate misleading marketing, such as HEPA-like and HEPA-style.
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Asthma facts and figures | Asthma and Allergy Foundation of America
What is a HEPA filter? | United States Environmental Protection Agency
Air cleaners: What you need to know | Asthma and Allergy Foundation of America
Air filters | EWG's Health Living
Cotinine factsheet | Centers for Disease Control and Prevention
Efficacy of portable air cleaners and masking for reducing indoor exposure to simulated exhaled SARS-CoV-2 aerosols — United States, 2021 | Centers for Disease Control and Prevention
Residential air cleaners - A technical summary | United States Environmental Protection Agency
Peak Flow Measurement | Johns Hopkins medicine
Filteration and disinfection FAQ | Ashrea.org
Health effects of ozone pollution | United States Environmental Protection Agency