Preventing COVID-19 spread with good air circulation

COVID-19 virus primarily spreads through people breathing it in, or by people touching contaminated surfaces and then touching their faces. The virus gets into the air best through people sneezing or coughing, but can also be released by talking (especially loud talking or singing), or even breathing (especially heavy breathing). The virus can build up to infective doses in indoor air if there is not good air circulation. With good air circulation, old indoor air is frequently replaced by new outdoor air. The old indoor air is sent outside, where any concentration of virus is quickly diluted to a much safer level.

Here are simple steps you can take to improve air circulation:

  • For spaces with windows, open the windows, especially when people are in the space.
  • Open outdoor air dampers as much as possible to get outdoor air into the building.
  • Check to make sure all exhausts are working. Many of the exhausts are in the restrooms.  This is easy check: hold a piece of toilet tissue paper to the exhaust. If it DOESN’T pull onto the exhaust’s surface, then the exhaust isn't working.
  • Turn thermostat settings to the "ON" position to have air moving through the system and filter at all times. 
  • Have your HVAC/ventilation serviced, including filter changes, coil cleanings, and drain pan free of obstructions.
  • If your system can accommodate them, use MERV13 or higher rated filters

Here are some sources supporting this, and providing related information:


Ventilation consideration when re-opening buildings
Related to this, here is CDC guidance about ventilation consideration when re-opening buildings, primarily focused on preventing mold, from https://www.cdc.gov/coronavirus/2019-ncov/php/building-water-system.html.

  1. After a building is reopened and occupied, routine (e.g., weekly) checks of the HVAC system are recommended to ensure operating efficiency.
  2. During HVAC checks, inspect and replace filters as indicated or needed.
  3. The frequency of HVAC system checks can be gradually reduced (e.g., monthly, quarterly), depending on the operational and maintenance specifications for the HVAC system.
  4. Maintain indoor temperature and relative humidity within ranges recommended in ASHRAE Standard 55-2017, Thermal Environmental Conditions for Human Occupancyexternal icon.
  5. If no routine HVAC operation and maintenance program is in place for the building, one should be developed and implemented. At a minimum, consider including the following:
    • Inspection and maintenance of HVAC components
    • Calibration of HVAC system controls
    • HVAC testing and balancing

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