Air Purifier Guide

Guide

Do Air Purifiers Help with COVID and Airborne Viruses?

By Dr. Alex Chen · Updated 2026-03-16

By Dr. James Park, Indoor Air Quality Specialist | Last updated: March 2026

Featured Snippet: Yes, HEPA air purifiers help reduce COVID-19 and airborne virus transmission indoors. True HEPA filters capture 99.97% of particles at 0.3 microns, including the respiratory aerosols (0.3–5 microns) that carry SARS-CoV-2. The CDC, WHO, and EPA all recommend portable HEPA air cleaners as one layer of protection — but they are not a substitute for vaccination, ventilation, or masking in high-risk situations.

Table of Contents

Affiliate Disclosure: AirPurifierReport.com is reader-supported. When you purchase through links on this page, we may earn an affiliate commission at no additional cost to you. Our recommendations are based on independent research and testing — we only recommend products that meet our editorial standards. Full disclosure.

How COVID-19 and Respiratory Viruses Spread Through Aerosols

Understanding how respiratory viruses travel through indoor air is the foundation for evaluating whether an air purifier can actually help. For years, the dominant public health messaging focused on large respiratory droplets — the visible spray from a cough or sneeze that falls to surfaces within 3–6 feet. That framework shaped early COVID-19 guidance around handwashing, surface disinfection, and the 6-foot distancing rule.

But the science shifted dramatically. By mid-2021, the overwhelming body of evidence confirmed what aerosol scientists had argued from the beginning: SARS-CoV-2 spreads primarily through aerosols — tiny respiratory particles smaller than 5 microns that remain suspended in indoor air for minutes to hours.

Droplets vs Aerosols: The Critical Distinction

When an infected person breathes, speaks, sings, coughs, or sneezes, they release a spectrum of respiratory particles ranging from less than 1 micron to over 100 microns in diameter. The physics of these particles determine their behavior:

  • Large droplets (>100 microns): Fall to the ground within seconds due to gravity. Travel no more than 1–2 meters. These are what the original 6-foot distancing rule was designed to address.
  • Medium droplets (5–100 microns): May remain airborne briefly but settle within seconds to minutes depending on air currents.
  • Aerosols (<5 microns): Remain suspended in indoor air for 30 minutes to several hours. Travel well beyond 6 feet and accumulate in poorly ventilated spaces. These particles follow air currents like smoke.

Research published in Science (2021) by Greenhalgh et al. established ten lines of evidence supporting aerosol transmission of SARS-CoV-2. Superspreader events in restaurants, choir practices, buses, and offices consistently showed transmission patterns that could only be explained by aerosol spread — not droplet or surface contact.

Why Indoor Spaces Are High-Risk

Outdoors, aerosols disperse rapidly into the vast volume of open air, diluting viral concentrations to levels that rarely cause infection. Indoors, the equation reverses. A single infected person in a poorly ventilated room can fill the space with virus-carrying aerosols within 15–30 minutes. Without ventilation or filtration, those aerosols accumulate over time, increasing the infection risk for everyone in the room.

This is where air purifiers enter the picture. A properly sized HEPA air purifier reduces the concentration of virus-carrying aerosols by continuously filtering room air — effectively simulating the dilution effect of outdoor ventilation. It does not eliminate risk, but it measurably reduces the dose of virus particles that occupants inhale.

The same aerosol transmission mechanism applies to influenza, RSV, measles, and other respiratory viruses. An air purifier for COVID protection also provides meaningful protection against the broader spectrum of airborne respiratory illnesses that circulate seasonally.

HEPA Filtration vs Virus Particle Size

One of the most persistent misconceptions about HEPA air purifiers and viruses is the particle size argument. The reasoning goes like this: SARS-CoV-2 is approximately 0.1 microns in diameter, HEPA filters are rated at 0.3 microns, therefore the virus passes right through. This sounds logical but is fundamentally wrong, and understanding why requires a brief look at how HEPA filtration actually works.

How HEPA Filters Actually Capture Particles

HEPA (High-Efficiency Particulate Air) filters do not work like a kitchen sieve with holes of a fixed size. They use a dense mat of randomly arranged fibers that capture particles through four distinct physical mechanisms:

  1. Interception: Particles following an airstream come within one radius of a fiber and are captured by van der Waals forces. Effective for mid-size particles (0.1–1.0 microns).
  2. Impaction: Larger, heavier particles cannot follow the curved airstream around fibers and collide directly. Effective for particles above 0.5 microns.
  3. Diffusion: The smallest particles (<0.1 microns) exhibit Brownian motion — random zigzag movement caused by collisions with air molecules — which dramatically increases their contact probability with filter fibers. This is why HEPA filters are actually more efficient at capturing very small particles, not less.
  4. Electrostatic attraction: Charged particles are attracted to oppositely charged fibers.

The 0.3-micron specification is not the upper limit of what HEPA filters can capture. It is the Most Penetrating Particle Size (MPPS) — the size at which filtration efficiency is at its minimum. At 0.3 microns, the interplay between diffusion (which decreases with particle size) and impaction/interception (which increases with particle size) creates a valley of lowest efficiency. A True HEPA filter must capture 99.97% of particles even at this most-difficult size.

For particles smaller than 0.3 microns — including free-floating virions at 0.1 microns — diffusion takes over and efficiency actually increases. For particles larger than 0.3 microns, impaction and interception dominate and efficiency also increases. The 0.3-micron rating represents the worst-case scenario, not a limitation.

The Virus Does Not Travel Alone

Even if HEPA filtration physics were not on our side (they are), there is a second critical fact: SARS-CoV-2 does not float through the air as a naked 0.1-micron virion. The virus is always encapsulated within a respiratory aerosol droplet, typically ranging from 0.3 to 5+ microns in diameter. These aerosol particles contain mucus, salts, proteins, surfactants, and water from the respiratory tract — along with the virus.

NASA-funded research conducted at the Johnson Space Center confirmed that HEPA filtration removes 99.97%+ of SARS-CoV-2-sized aerosols from air. A 2021 study published in Aerosol Science and Technology demonstrated that portable HEPA air purifiers reduced aerosol concentrations by 65–90% in occupied rooms, depending on placement and CADR relative to room size.

H13 vs H14 HEPA: Does the Grade Matter?

For virus protection specifically, both H13 (99.97% at MPPS) and H14 (99.995% at MPPS) HEPA grades provide excellent aerosol filtration. The practical difference in a home setting is minimal. H14 filters appear in medical-grade units like the IQAir HealthPro Plus and are worth considering for high-risk households, but H13 True HEPA is the baseline standard that delivers effective virus aerosol reduction.

What matters more than H13 vs H14 in real-world virus protection is CADR — how quickly the purifier processes the room's air volume. A high-CADR H13 unit outperforms a low-CADR H14 unit every time, because air changes per hour determine how quickly virus-carrying aerosols are removed from breathing zones.

What the CDC and WHO Recommend

Both the CDC and WHO have issued explicit guidance on using portable air cleaners for COVID-19 and respiratory virus protection. These are not vague suggestions — they are specific, actionable recommendations backed by the agencies' technical review of the evidence.

CDC Guidance

The CDC's guidance on ventilation in buildings states: "When used properly, air purifiers can help reduce airborne contaminants including viruses in a home or confined space." The agency specifically recommends portable HEPA air cleaners and emphasizes the following points:

  • Use a portable HEPA air cleaner in rooms where ventilation with outdoor air is limited
  • Choose a unit with a CADR appropriate for the room size
  • Place the unit in the room where people spend the most time
  • Run the unit continuously on the highest setting that is tolerable for noise
  • For isolation rooms (when a household member is infected), use a HEPA air purifier in the sick person's room with the door closed

The CDC also endorses DIY Corsi-Rosenthal boxes as an effective, low-cost alternative to commercial HEPA units — particularly useful for schools, community centers, and households that cannot afford commercial purifiers.

WHO Guidance

The WHO's roadmap for improving and ensuring good indoor ventilation (published March 2023, updated 2025) recommends portable air cleaners with HEPA filters as a supplemental measure when adequate mechanical ventilation is not available. The WHO emphasizes that air cleaning should be combined with other interventions — not used as a standalone solution.

EPA Guidance

The EPA's Indoor Air and COVID-19 guidance recommends portable HEPA air cleaners and notes: "Portable air cleaners and HVAC filters can reduce indoor air pollutants, including viruses, that are airborne. By themselves, portable air cleaners and HVAC filters are not enough to protect people from the virus that causes COVID-19," reinforcing the layered-protection approach.

The consistency across all three agencies is clear: HEPA air purifiers work, they help, and they should be part of your indoor air strategy — but they are not a replacement for other protective measures.

Which Air Purifiers Actually Work Against Viruses

Not every air purifier marketed for "germ protection" or "virus removal" delivers meaningful results. For effective airborne virus reduction, two specifications are non-negotiable: True HEPA filtration (H13 or H14) and a CADR high enough to deliver 5–6 air changes per hour in your target room.

Key Specifications for Virus Protection

  • True HEPA (H13 minimum): Must capture 99.97% at 0.3 microns. Reject "HEPA-type" or "HEPA-style" filters.
  • CADR 200+ CFM: For a typical 200–300 sq ft bedroom. Larger rooms need proportionally higher CADR.
  • Low noise on high setting: You need to run the purifier on high continuously, so noise under 55 dB on max is ideal.
  • No ozone emission: Avoid ionizers and plasma generators, or ensure they can be disabled.

If you are also looking for a purifier that handles allergens and pet dander, our guide on the best air purifier for pet dander covers models that overlap with our virus protection picks.

1. Coway Airmega 400S — Best Overall

The Coway Airmega 400S combines a True HEPA filter with excellent CADR across all particle sizes. Its dual-intake design processes air from both sides simultaneously, and smart features allow app control and real-time air quality monitoring.

  • CADR: 350 CFM (smoke) / 400 CFM (dust)
  • Room size: Up to 700 sq ft (delivers ~5 ACH in 450 sq ft)
  • Noise: 22–52 dB
  • Price: ~$450
  • Filter replacement: Every 12 months (~$80/year)

Check price on Amazon{: .cta-button}

2. IQAir HealthPro Plus — Best Medical-Grade Protection

The IQAir HealthPro Plus uses a HyperHEPA filter (H12/H13 equivalent) tested to capture particles down to 0.003 microns with 99.5%+ efficiency. It contains 5 lbs of granular activated carbon for VOC removal and is used in hospitals, clinics, and clean rooms worldwide. This is the unit I recommend for immunocompromised households.

  • CADR: 300 CFM
  • Room size: Up to 1,125 sq ft
  • Noise: 22–59 dB
  • Price: ~$900
  • Filter replacement: Every 18–24 months (~$130/cycle)

Check price on Amazon{: .cta-button}

3. Levoit Core 600S — Best Value

The Levoit Core 600S delivers premium CADR at a mid-range price point. It features True HEPA H13 filtration, VortexAir Technology 3.0, and smart app integration. For households looking for strong virus protection without the IQAir price tag, this is the sweet spot.

  • CADR: 310 CFM (smoke) / 410 CFM (dust)
  • Room size: Up to 635 sq ft
  • Noise: 24–55 dB
  • Price: ~$230
  • Filter replacement: Every 8–10 months (~$70/cycle)

Check price on Amazon{: .cta-button}

4. Winix 5500-2 — Best Budget Option

The Winix 5500-2 uses a True HEPA filter and includes a washable AOC carbon filter. It has a built-in PlasmaWave ionizer, but this feature can be disabled — and should be during active illness in the household to avoid ozone interactions with cleaning chemicals.

  • CADR: 232 CFM (smoke) / 243 CFM (dust)
  • Room size: Up to 360 sq ft
  • Noise: 28–56 dB
  • Price: ~$160
  • Filter replacement: Every 12 months (~$60/year)

Check price on Amazon{: .cta-button}

5. Medify MA-40 — Best for Medium Rooms

The Medify MA-40 features H13 True HEPA filtration with a dual-filter design and solid CADR performance. It includes a built-in air quality sensor and three fan speeds. The clean design fits well in bedrooms and home offices.

  • CADR: 330 CFM (smoke)
  • Room size: Up to 840 sq ft
  • Noise: 25–56 dB
  • Price: ~$280
  • Filter replacement: Every 8–10 months (~$60/cycle)

Check price on Amazon{: .cta-button}

Comparison Table

Model CADR (Smoke) Room Size Noise (dB) HEPA Grade Price Best For
Coway Airmega 400S 350 CFM 700 sq ft 22–52 H13 ~$450 Best overall
IQAir HealthPro Plus 300 CFM 1,125 sq ft 22–59 H12/H13 ~$900 Immunocompromised
Levoit Core 600S 310 CFM 635 sq ft 24–55 H13 ~$230 Best value
Winix 5500-2 232 CFM 360 sq ft 28–56 H13 ~$160 Budget pick
Medify MA-40 330 CFM 840 sq ft 25–56 H13 ~$280 Medium rooms

For large open-plan spaces, you may need multiple units or a single high-CADR model. Our guide on the best air purifiers for large rooms covers that scenario in detail.

UV-C Air Purifiers: Do They Kill Viruses?

UV-C light at 254 nanometers is a proven germicidal technology used in hospitals, water treatment, and laboratory settings. The mechanism is well-understood: UV-C photons damage the RNA and DNA of microorganisms, rendering them unable to replicate. SARS-CoV-2 is an RNA virus and is susceptible to UV-C inactivation.

However, the effectiveness of UV-C in consumer air purifiers is a separate question from UV-C effectiveness in controlled laboratory settings.

The Exposure Time Problem

UV-C inactivation depends on dose, which is a function of intensity (measured in millijoules per square centimeter) and exposure time. Laboratory studies typically expose virus samples to UV-C for 10–30 seconds at close range. Inside a consumer air purifier, air moves past the UV-C bulb at speed — often in less than 0.5 seconds. This dramatically reduces the UV-C dose each particle receives.

Some commercial purifiers with UV-C chambers claim 99%+ virus kill rates, but independent testing often shows significantly lower real-world performance when airflow is factored in. The faster the fan speed (which you want for high CADR), the less UV-C exposure time each particle receives.

Combination Units: HEPA + UV-C

The most practical approach is a unit that combines True HEPA filtration with a UV-C chamber. In this design, the HEPA filter captures the virus-carrying aerosol, and the UV-C light provides additional inactivation of pathogens on the filter surface. This is a reasonable belt-and-suspenders approach, though the HEPA filter is doing the heavy lifting.

The GermGuardian AC4825 and similar HEPA + UV-C combination units are popular, but their CADR ratings are typically lower (100–150 CFM) than the pure HEPA units in our recommended list. For virus protection, prioritize CADR and HEPA grade over UV-C features.

Ionizers and Plasma: Marketing vs Reality

Ionizers, bipolar ionization, plasma wave technology, photocatalytic oxidation (PCO), and similar "active" air purification technologies are aggressively marketed for virus and pathogen protection. The claims are often impressive. The evidence, unfortunately, is not.

How Ionizers Work (In Theory)

Ionizers release charged ions (positive, negative, or both in bipolar ionization) into the air. These ions attach to airborne particles, causing them to clump together and settle onto surfaces or become charged enough to stick to collection plates. Some manufacturers claim that ions directly damage viral envelopes and deactivate pathogens.

The Evidence Gap

The fundamental problem with ionizer-based virus claims is the gap between laboratory conditions and real-world indoor environments. Most ionization studies cited by manufacturers are conducted in small test chambers (often less than 1 cubic meter) with high ion concentrations, no air mixing, and controlled conditions that do not represent an actual room.

In real rooms with furniture, air currents, varying humidity, and continuous aerosol generation from breathing, the ion concentrations produced by consumer devices are orders of magnitude lower than what the chamber tests used. A 2022 review published in Science and Technology for the Built Environment found that "evidence for bipolar ionization reducing pathogen exposure in occupied buildings is limited and inconsistent."

Ozone Concerns

Many ionization and plasma technologies produce ozone as a byproduct. While the amounts are typically small, ozone is a potent respiratory irritant even at low concentrations. The EPA states that ozone concentrations that would be needed to disinfect air of viruses would far exceed safe human exposure limits. Running an ozone-generating device in a room with a sick person — whose respiratory system is already compromised — is counterproductive.

The bottom line: if your primary goal is reducing airborne virus concentration, spend your budget on a True HEPA air purifier with high CADR. Ionization and plasma technologies are not supported by sufficient real-world evidence for virus protection.

What Air Purifiers CANNOT Do

As an indoor air quality specialist, I believe it is just as important to be clear about the limitations of air purifiers as it is to explain their benefits. Overstating what an air purifier can do is not just misleading — it can create a false sense of security that increases risk.

Air Purifiers Are One Layer, Not the Whole Solution

The concept of layered protection (sometimes called the Swiss cheese model) applies directly to respiratory virus defense. Each layer has holes — no single measure is 100% effective. But when you stack multiple layers, the holes do not align, and your overall protection is strong.

  • Vaccination: Reduces severity of illness and lowers viral load in the respiratory tract, which means fewer and less concentrated aerosols emitted.
  • Ventilation: Dilutes aerosol concentration by replacing indoor air with outdoor air. Open windows, HVAC systems, and exhaust fans all contribute.
  • Air purification: Removes aerosols from indoor air through filtration. Supplements ventilation but cannot replace it entirely.
  • Masking: Reduces aerosol emission at the source and provides filtration for the wearer during inhalation. Most effective in close-contact, high-risk situations.
  • Distancing and reduced occupancy: Lowers the aerosol dose in your immediate breathing zone.

An air purifier operates on only one of these layers. It reduces the concentration of virus-carrying aerosols in room air but does not prevent every mode of transmission.

Specific Limitations

  • Contact transmission: An air purifier does nothing to prevent virus transfer from contaminated surfaces to your hands to your mucous membranes.
  • Close-range aerosol exposure: If you are within 1–2 feet of an infected person, you are inhaling their respiratory output directly before the room air purifier has a chance to process it.
  • Continuous aerosol generation: In a room where an infected person is continuously breathing or talking, the air purifier is in a constant race to remove aerosols as they are generated. It reduces concentration but cannot eliminate it.
  • Compliance and operation: An air purifier only works when it is running, on the right setting, with a clean filter, in the right location. A unit sitting in the corner on low with a clogged filter provides negligible protection.

For comprehensive allergy and respiratory protection beyond viruses, our guide on the best air purifier for allergies covers complementary considerations.

How to Size an Air Purifier for Virus Protection

For general air quality improvement, manufacturers' room size ratings (based on 2 ACH) are adequate. For virus protection, you need to think differently. The goal is to achieve 5–6 air changes per hour (ACH), which is the threshold recommended by the CDC and ASHRAE for meaningful airborne pathogen reduction.

The ACH Formula

Air changes per hour tells you how many times the total volume of air in a room is processed through filtration each hour.

ACH = (CADR in CFM × 60) ÷ Room Volume in Cubic Feet

Where Room Volume = Length (ft) × Width (ft) × Ceiling Height (ft)

To work backward from your target ACH to the required CADR:

Required CADR (CFM) = (Room Volume × Target ACH) ÷ 60

Worked Example

Suppose you have a 12 ft × 15 ft bedroom with 8-foot ceilings and you want 5 ACH for virus protection:

  • Room volume = 12 × 15 × 8 = 1,440 cubic feet
  • Required CADR = (1,440 × 5) ÷ 60 = 120 CFM

For the same room at 6 ACH (higher protection):

  • Required CADR = (1,440 × 6) ÷ 60 = 144 CFM

Even a budget model like the Winix 5500-2 (232 CFM smoke CADR) delivers nearly 10 ACH in this bedroom — excellent virus protection. But in a 500 sq ft living room with 8-foot ceilings (4,000 cubic feet), you would need 333 CFM to hit 5 ACH, making a higher-CADR model like the Coway Airmega 400S necessary.

Quick Reference Table: CADR Needed by Room Size

Room Size (sq ft) Volume (8 ft ceiling) CADR for 5 ACH CADR for 6 ACH
150 1,200 cu ft 100 CFM 120 CFM
200 1,600 cu ft 133 CFM 160 CFM
300 2,400 cu ft 200 CFM 240 CFM
400 3,200 cu ft 267 CFM 320 CFM
500 4,000 cu ft 333 CFM 400 CFM
700 5,600 cu ft 467 CFM 560 CFM

Rooms above 500 sq ft often require two units or a single high-CADR commercial-grade purifier to reach virus-protective ACH levels.

Best Practices for Using Air Purifiers During Illness

When someone in your household is actively sick with COVID or another respiratory illness, how you use your air purifier matters as much as which unit you own. These practices are drawn from CDC guidance and aerosol science principles.

Isolation Room Setup

If the sick person can be isolated in a single room with the door closed, this is the highest-impact configuration:

  1. Place a HEPA air purifier in the sick person's room. Position it 3–6 feet from where the person rests, with the air intake facing toward the bed and no obstructions on any side. Do not place it in a corner or behind furniture.
  2. Keep the door closed. A closed door with a running HEPA purifier creates negative-pressure-like conditions that reduce aerosol leakage to the rest of the home, especially if there is a gap under the door.
  3. Run the purifier on the highest tolerable setting continuously — 24/7. Do not turn it off when the sick person sleeps. If noise is an issue, a model with low noise on high (like the Coway Airmega 400S at 52 dB) makes continuous high-speed operation realistic.
  4. If the sick person must leave the room (bathroom trips, etc.), leave the purifier running in the room. It will continue clearing residual aerosols. The room air will be substantially cleaner within 15–30 minutes of the person leaving.

Placement Tips

  • Position the purifier so its clean air output blows toward the center of the room or toward the occupant's breathing zone — not toward a wall.
  • Keep the unit at least 1 foot from walls and furniture on all sides to avoid airflow restriction.
  • Elevate the unit to table height if possible. Aerosols concentrate in the breathing zone (3–5 feet above floor level), and purifiers perform better when their intake is closer to this zone.
  • Do not place the purifier directly between two people in a shared room, as the airflow could pull aerosols from the infected person's side toward the clean side.

Filter Management

During active illness, your HEPA filter is capturing a high concentration of virus-carrying aerosols. When replacing filters:

  • Wear a mask and disposable gloves when removing used filters.
  • Seal the used filter in a plastic bag before disposing of it.
  • Wash your hands thoroughly after filter replacement.
  • HEPA-captured viruses become inactive on the filter over time (typically within hours to days), but handling precautions are prudent during active illness.

FAQ

Do air purifiers help with COVID-19?

Yes. True HEPA air purifiers capture 99.97% of airborne particles at 0.3 microns, including the respiratory aerosols (0.3–5 microns) that carry SARS-CoV-2. The CDC and EPA both recommend portable HEPA air cleaners as one layer of protection against COVID-19 transmission indoors. They reduce the concentration of virus-carrying aerosols but should be combined with ventilation, vaccination, and other measures.

What type of air purifier kills COVID?

HEPA air purifiers do not kill COVID — they physically capture virus-carrying aerosol particles in the filter media. UV-C air purifiers can inactivate viruses but require sufficient exposure time, which most consumer units do not provide at high fan speeds. True HEPA (H13 or H14) with a high CADR is the most reliable technology for reducing airborne virus concentration indoors.

Can HEPA filters capture the COVID virus?

SARS-CoV-2 is approximately 0.1 microns, but the virus does not float freely in the air. It travels inside respiratory aerosol droplets ranging from 0.3 to 5+ microns. HEPA filters capture 99.97% of particles at 0.3 microns — the most penetrating particle size — and are even more efficient at sizes above and below that threshold due to impaction and diffusion mechanisms.

How many air changes per hour do I need for virus protection?

The CDC recommends 5 or more air changes per hour (ACH) for effective airborne infection reduction. ASHRAE recommends 6+ ACH equivalent for higher-risk settings. Use the formula: Required CADR = (Room volume in cubic feet x Target ACH) / 60 to determine the right purifier size.

Are ionizers effective against COVID?

Ionizers and plasma-based purifiers have limited independent evidence supporting their effectiveness against viruses in real-world conditions. Some produce ozone as a byproduct, which is a respiratory irritant. The CDC and EPA recommend HEPA filtration over ionization for airborne virus reduction. If your purifier has an ionizer feature, consider disabling it during illness.

Should I run an air purifier 24/7 during COVID?

Yes. For maximum protection, run your HEPA air purifier continuously on the highest comfortable setting. Virus-carrying aerosols can remain suspended in indoor air for hours, and concentration rebuilds quickly when filtration is paused. During active illness in the household, continuous high-speed operation in the sick person's room is strongly recommended.

Can an air purifier replace a mask or vaccine for COVID protection?

No. Air purifiers are one layer of a multi-layered protection strategy. They reduce airborne virus concentration but cannot eliminate transmission risk entirely. Vaccination remains the most important protection against severe illness. Masking provides direct source control and wearer protection in close-contact situations. The CDC describes air cleaning as a supplemental measure, not a replacement for these other interventions.

Sources & Methodology

  1. CDC. "Ventilation in Buildings." Centers for Disease Control and Prevention. Updated 2025. cdc.gov/coronavirus/ventilation
  2. WHO. "Roadmap to Improve and Ensure Good Indoor Ventilation in the Context of COVID-19." World Health Organization, March 2023 (updated 2025). who.int
  3. EPA. "Indoor Air and COVID-19." United States Environmental Protection Agency. Updated 2025. epa.gov/coronavirus/indoor-air-and-covid-19
  4. Greenhalgh T, et al. "Ten Scientific Reasons in Support of Airborne Transmission of SARS-CoV-2." The Lancet, 2021; 397(10285): 1603–1605. doi.org/10.1016/S0140-6736(21)00869-2
  5. ASHRAE. "ASHRAE Position Document on Filtration and Air Cleaning." American Society of Heating, Refrigerating and Air-Conditioning Engineers, 2021 (updated 2024). ashrae.org
  6. Curtius J, Granzin M, Schrod J. "Testing mobile air purifiers in a school classroom: Reducing the airborne transmission risk for SARS-CoV-2." Aerosol Science and Technology, 2021; 55(5): 586–599. doi.org/10.1080/02786826.2021.1877257
  7. Lindsley WG, et al. "Efficacy of Portable Air Cleaners and Masking for Reducing Indoor Exposure to Simulated Exhaled SARS-CoV-2 Aerosols." MMWR Morbidity and Mortality Weekly Report, CDC, 2021; 70(27): 972–976. doi.org/10.15585/mmwr.mm7027e1
  8. Morawska L, et al. "How can airborne transmission of COVID-19 indoors be minimised?" Environment International, 2020; 142: 105832. doi.org/10.1016/j.envint.2020.105832
  9. California Air Resources Board (CARB). "Certified Air Cleaning Devices." ww2.arb.ca.gov/list-carb-certified-air-cleaning-devices

This article is for informational purposes only and does not constitute medical advice. Consult your healthcare provider for guidance specific to your health situation. Air purifiers are one component of a comprehensive respiratory virus protection strategy and should not replace vaccination, medical treatment, or public health guidance.