Because COVID-19 is transmitted through contact with respiratory fluids that carry the infectious SARS-CoV-2 virus, an infected person can be exposed by coughing or talking near them. They can also be exposed by inhaling aerosol particles that spread away from the infected person. Airborne transmission of COVID-19 can occur over distances greater than six feet. Particles from an infected person can move around an entire room or interior space.
Particles can also remain in the air after a person has left the room; in some cases, they can stay in the air for hours. A person can also be exposed through splashes and aerosols of respiratory fluids directly on the mucous membranes. Spread can also sometimes occur through contact with contaminated surfaces, although this route is now considered to be less likely. See scientific and technical resources related to indoor air and coronavirus (COVID-19) or indoor air and key COVID-19 publications for technical information.
In the typical American house with a central air conditioning system, there is no option to use outdoor air. In households where everyone is healthy, this is fine, but in households where someone has the new coronavirus or has been exposed to the virus, this can be dangerous. Reoccupying a building during the COVID-19 pandemic should not, in most cases, require new building ventilation systems. However, upgrades or upgrades to the ventilation system can increase the supply of clean air and dilute potential contaminants.
Consult experienced heating, ventilation and air conditioning (HVAC) professionals when considering changes to HVAC systems and equipment. Buildings that provided healthy and code-compliant indoor air quality before the pandemic can be improved for pandemic occupancy through less costly interventions. Below is a list of ventilation interventions that can help reduce the concentration of virus particles in the air. They represent a list of “tools” in the mitigation toolbox, each of which can contribute to risk reduction.
Implementing multiple tools at the same time is consistent with CDC's stratified approach and will increase the overall effectiveness of ventilation interventions. These ventilation interventions may reduce the risk of exposure to the virus and reduce the spread of the disease, but they will not eliminate the risk completely. Then there is the transmission of aerosols when an infected person expels microscopic infectious particles so small that they remain in the air and spread from person to person in air currents. In a house with a sick person, Chen recommends turning off the air and opening a window, because the air conditioning system could easily circulate coronavirus droplets from one room in the house to another.
Scientists say very little research has been done on the role of heating, ventilation and air conditioning systems in the spread of coronavirus. At home, the risk of contracting COVID-19 through drafts or air conditioning units is no more likely to spread the virus through close contact or touching contaminated surfaces. If someone in your household has tested positive for coronavirus infection, it's best to keep them in a separate room, away from other people in the household, says CDC. The layout and design of a building, as well as the occupancy and type of heating, ventilation and air conditioning (HVAC) system, can affect the possible spread of the virus through the air.
Public health experts have warned for months about the possibility of airborne transmission or the spread of the virus through tiny exhaled particles (aerosols) that can stay in the indoor air and travel longer than 6 feet. In addition, opening a window can help bring in fresh air from outside and disperse stale air indoors, and that could help reduce the possibility of spreading virus particles around the house. In the article, Chinese researchers tracked an outbreak of COVID-19 in airflow in an air-conditioned restaurant and recommended increasing the distance between tables and improving ventilation. In comparison, if you were outdoors and close to an infected person who exhaled some viral particles, there is a much larger volume of air that flows to disperse and dilute those particles quickly, reducing the risk of spreading to another person nearby.
Also, if you haven't had a flow of people in and out of your home, the only droplets that could spread through the air conditioner are yours and those of anyone else in your house. A central air conditioning system uses a fan to draw warm air from the room into a return vent, blowing it through coils that absorb heat and cool the air. Cold weather in the winter, which similarly forces people to enter and increase heat, also creates a poorly ventilated environment in which viral particles can spread through the air and cause infections. .