Science and Technical Resources related to Indoor Air and Coronavirus (COVID-19)
The importance of different routes of transmission for SARS-CoV-2 is an ongoing area of research. SARS-CoV-2 can remain airborne in indoor environments for hours, potentially increasing in concentration over time. Therefore, unless adequate precautions are taken, the longer a space is occupied and the more people that are present, the greater the potential for airborne transmission of the virus (See also Key References on Indoor Air and COVID-19).
As a result, lowering the concentration of SARS-CoV-2 by means of ventilation and filtration can play a role in controlling transmission of the virus that causes COVID-19. In addition to physical distancing, adequate ventilation, wearing masks, and avoidance of crowded indoor spaces can play a role in controlling transmission of the virus. Consult guidance from the Centers for Disease Control and Prevention (CDC) and local authorities on current guidelines on the use of masks. Ventilation is also a critical measure that can be taken to reduce exposure to cleaning products, disinfectants, and the byproducts they produce as a result of chemical reactions in indoor air.
Links to additional information:
- Read the CDC scientific brief: SARS-CoV-2 and Surface (Fomite) Transmission for Indoor Community Environments
CDC has stated: People can be infected with SARS-CoV-2 through contact with surfaces. However, based on available epidemiological data and studies of environmental transmission factors, surface transmission is not the main route by which SARS-CoV-2 spreads, and the risk is considered to be low.
- Read the EPA Science Advisory Board Report: Review of COVID-19 Pandemic Scientific and Technical Issues to Inform EPA’s Research Activities
The EPA SAB has stated: "There is evidence that inhalation of expelled aerosol from infected individuals is potentially a significant pathway in the spread of SARS-CoV-2 (Alford, 1966; Douglas, 1975; Little, 1979; Tellier, 2006). The SAB presented some of this evidence as part of the public teleconference on April 30, 2020 (Jayjock, 2020). A continuum of particle sizes ranging from less than 1 micron to over 1,400 microns is emitted when people cough, sneeze, speak or exhale (Nicas, 2005; Chao, 2009; Lindsley, 2010; Milton, 2013; Bourouiba, 2014; Skaria, 2014; MacIntyre, 2016; Bourouiba, 2020). These particles can deposit into the deepest part of the lung, the alveoli (Milton, 2013; Lindsley, 2010)."
CDC has stated: "COVID-19 can sometimes be spread by airborne transmission. Some infections can be spread by exposure to virus in small droplets and particles that can linger in the air for minutes to hours. These viruses may be able to infect people who are further than 6 feet away from the person who is infected or after that person has left the space. This kind of spread is referred to as airborne transmission and is an important way that infections like tuberculosis, measles, and chicken pox are spread."
CDC has stated:
“Modes of SARS-CoV-2 transmission are now categorized as inhalation of virus, deposition of virus on exposed mucous membranes, and touching mucous membranes with soiled hands contaminated with virus.”
“Although how we understand transmission occurs has shifted, the ways to prevent infection with this virus have not.”
“The principal mode by which people are infected with SARS-CoV-2 (the virus that causes COVID-19) is through exposure to respiratory fluids carrying infectious virus. Exposure occurs in three principal ways: (1) inhalation of very fine respiratory droplets and aerosol particles, (2) deposition of respiratory droplets and particles on exposed mucous membranes in the mouth, nose, or eye by direct splashes and sprays, and (3) touching mucous membranes with hands that have been soiled either directly by virus-containing respiratory fluids or indirectly by touching surfaces with virus on them.”
- Read the ASHRAE Environmental Health Committee (EHC) Emerging Issue Brief: Pandemic COVID-19 and Airborne (PDF)
ASHRAE (formerly the American Society of Heating, Refrigerating and Air-Conditioning Engineers) has stated: “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.”
- Read the CDC report: Knowledge and Practices Regarding Safe Household Cleaning and Disinfection for COVID-19 Prevention — United States, May 2020
- Read the American Industrial Hygiene Association (AIHA) Covid-19 Resources
- Read the Federation of European Heating, Ventilation and Air Conditioning Associations (REHVA) Resources
- Watch the EPA IAQ Science Series Webinar: SARS-CoV-2 in Indoor Air: Principles and Scenarios
- Read the ASHRAE guidance: Reopening of schools and universities
Watch the National Academies of Sciences, Engineering, and Medicine (NASEM) 2 day virtual workshop: Airborne Transmission of the SARS-CoV-2, featuring presentations by experts in aerosol science, virology, infectious disease, and epidemiology.">