Air filters work – EPA, CDC, OSHA, ASHRAE, and more agree.

air filters work

We know that HEPA and MERV13 filters work to remove airborne virus particles. Read all about it from the EPA, CDC, OSHA, and ASHRAE.

EPA: United States Environmental Protection Agency

Air Cleaners, HVAC Filters, and Coronavirus (COVID-19)

“When used properly, air cleaners and HVAC filters can help reduce airborne contaminants including viruses in a building or small space.”

“Consider using portable air cleaners to supplement increased HVAC system ventilation and filtration, especially in areas where adequate ventilation is difficult to achieve.”

CDC: Centers for Disease Control and Prevention

Ventilation in Buildings

“SARS-CoV-2 viral particles spread between people more readily indoors than outdoors. Indoors, the concentration of viral particles is often higher than outdoors, where even a light wind can rapidly reduce concentrations. When indoors, ventilation mitigation strategies can help reduce viral particle concentration. The lower the concentration, the less likely viral particles can be inhaled into the lungs (potentially lowering the inhaled dose); contact eyes, nose, and mouth; or fall out of the air to accumulate on surfaces. Protective ventilation practices and interventions can reduce the airborne concentrations and reduce the overall viral dose to occupants.”

“Use portable high-efficiency particulate air (HEPA) fan/filtration systems to enhance air cleaning (especially in higher risk areas such as a nurse’s office or areas frequently inhabited by people with a higher likelihood of having COVID-19 and/or an increased risk of getting COVID-19).”

What is a HEPA filter and why use a portable HEPA air cleaner?
HEPA filters are no less than 99.97% efficient at capturing human-generated viral particles associated with SARS-CoV-2.

OSHA: Occupational Safety and Health Administration

Maintain Ventilation Systems.

“The virus that causes COVID-19 spreads between people more readily indoors than outdoors. Improving ventilation is a key engineering control that can be used as part of a layered strategy to reduce the concentration of viral particles in indoor air and the risk of virus transmission to unvaccinated and otherwise at-risk workers in particular. A well-maintained ventilation system is particularly important in any indoor workplace setting and when working properly, ventilation is an important control measure to limit the spread of COVID-19. Some measures to improve ventilation are discussed in CDC’s Ventilation in Buildings and in the OSHA Alert: COVID-19 Guidance on Ventilation in the Workplace. These recommendations are based on American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Guidance for Building Operations and Industrial Settings during the COVID-19 Pandemic. Adequate ventilation will protect all people in a closed space. Key measures include ensuring heating, ventilation, and air conditioning (HVAC) systems are operating in accordance with the manufacturer’s instructions and design specifications, conducting all regularly scheduled inspections and maintenance procedures, maximizing the amount of outside air supplied, installing air filters with a Minimum Efficiency Reporting Value (MERV) 13 or higher where feasible, maximizing natural ventilation in buildings without HVAC systems by opening windows or doors, when conditions allow (if that does not pose a safety risk), and considering the use of portable air cleaners with High Efficiency Particulate Air (HEPA) filters in spaces with high occupancy or limited ventilation.”

ASHRAE: The American Society of Heating, Refrigerating and Air-Conditioning Engineers

Airborne Transmission Statement & Core Recommendations

ASHRAE Statement on airborne transmission of SARS-CoV-2:

  • Airborne transmission of SARS-CoV-2 is significant and should be controlled. Changes to building operations, including the operation of HVAC systems can reduce airborne exposures.

ASHRAE Statement on operation of heating, ventilating, and air-conditioning systems to reduce SARS-CoV-2 transmission:

  • Ventilation and filtration provided by heating, ventilating, and air-conditioning systems can reduce the airborne concentration of SARS-CoV-2 and thus the risk of transmission through the air. Unconditioned spaces can cause thermal stress to people that may be directly life threatening and that may also lower resistance to infection. In general, disabling of heating, ventilating, and air-conditioning systems is not a recommended measure to reduce the transmission of the virus.

ASHRAE Core Recommendations for Reducing Airborne Infectious Aerosol Exposure are available HERE.

        – MERV ≥13 (or ISO ePM1) are efficient at capturing airborne viruses
        – High efficiency particulate air (HEPA) filters are more efficient than MERV 16 filters.

“Aim to achieve filtration efficiency similar to a MERV 13 filter.”

ASHRAE PDF: In room air cleaner guidance for reducing covid-19 in air in your space or room.
When to use an in-room (separate from HVAC) air cleaner, and how to choose the right one.

Do HEPA Filters Really Catch Coronavirus Particles?
Columbia University News – November 11, 2021
(Also recommends Corsi-Rosenthal Boxes)

How to choose a HEPA air filter

Please see our portable air cleaner (HEPA filter) buying guide. Includes guidance on what to avoid.

How to build a MERV13 air filter

Please see our page on the DIY box fan air filter, also known as the “Corsi-Rosenthal box”. Includes an extensive FAQ.

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