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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 wearing masks, social distancing, cleaning and disinfection. 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:

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."

ASHRAE (formerly the American Society of Heating, Refrigerating and Air-Conditioning Engineers) has stated: “Transmission of SARS-CoV-2 through the air is sufficiently likely that airborne exposure to the virus should be controlled.” “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.”

The World Health Organization (WHO) has stated: “Airborne transmission of the virus can occur in health care settings where specific medical procedures, called aerosol generating procedures, generate very small droplets called aerosols. Some outbreak reports related to indoor crowded spaces have suggested the possibility of aerosol transmission, combined with droplet transmission, for example, during choir practice, in restaurants or in fitness classes.”

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