Roadmap to Improve & Ensure Good Indoor Ventilation in the Context of COVID-19 by WHO
Knowledge about transmission of the SARS-CoV-2 virus is continuously evolving as new evidence accumulates. According to available evidence, SARS-CoV-2 mainly spreads between people when an infected person is in close contact with another person. Transmissibility of the virus depends on the amount of viable virus being shed and expelled by a person, the type of contact they have with others, the setting and what IPC measures are in place.
The virus can spread from an infected person’s mouth or nose in small liquid particles when the person coughs, sneezes, sings, breathes heavily or talks. These liquid particles are different sizes, ranging from larger “respiratory droplets” to smaller “aerosols”. Close- range contact (typically within 1 m) can result in inhalation of, or inoculation with, the virus through the mouth, nose or eyes.
WHO has published numerous recommendations for measures to prevent spread of COVID-19, among which is ensuring good ventilation in indoor settings, including health care facilities, public spaces and residential areas. A well-designed, maintained and operated system can reduce the risk of COVID-19 spread in indoor spaces by diluting the concentration of potentially infectious aerosols through ventilation with outside air and filtration and disinfection of recirculated air.
This roadmap aims to define the key questions users should consider to assess indoor ventilation and the major steps needed to reach recommended ventilation levels or simply improve indoor air quality (IAQ) in order to reduce the risk of spread of COVID-19. It also includes recommendations on how to assess and measure the different parameters, specifically in health care, non-residential and residential settings. It is meant to be a technical document helping users to analyse building HVAC systems in order to implement, if required, the different strategies proposed to improve HVAC’s ability to mitigate and reduce the risk of COVID-19 transmission.
Read the document here.