COVID-19 vs. wildfire smoke: How to follow opposing safety guidelines

Ventilation guidance to protect people from SARS-CoV-2, the virus that causes COVID-19, and wildfire smoke, are completely opposite. Here's what you should know.

Like Rock'em Sock'em robots, ventilation guidance to protect people from SARS-CoV-2, the virus that causes COVID-19, and wildfire smoke, are completely opposite. 

Ventilation guidance for reducing SARS-CoV-2 aerosols indoors? Maximize the introduction of outdoor air, to 100% if possible.  

Ventilation guidance for reducing wildfire smoke indoors? Minimize introduction of outdoor air (even close off outdoor air and recirculate 100% indoor air).  

When COVID-19 is the primary concern, Oregon OSHA's guidance is clear. But if wildfire smoke is in your area, you also have to reduce employee exposures to wildfire smoke while minimizing the risk of SARS-Cov-2 spread.  

Public health guidance from the Centers for Disease Control and Prevention and the Oregon Health Authority doesn't address this conflict. So, what is a business to do?  

These would-be enemies of human health DO have something else in common: they can be controlled by way of filtration.


Filtration is your knockout punch for these worker health enemies. 

The air we breathe needs to be free of health hazards, including viruses and wildfire smoke particles. The good news is that filtration works for both. The key is filtering at the right efficiency.  

To protect your workforce when dealing with COVID-19 and wildfire smoke hazards, consider these options: 

  1. Reduce building occupancy, which reduces potential sources of COVID-19 hazards and those who may be exposed to wildfire smoke. Consider remote work, creative scheduling, or workflow/space redesign. Plan ahead to further reduce occupancy quickly while maintaining essential operations and services when wildfire smoke conditions worsen. 
  2. Filter, filter, filter. Use indoor HEPA filter units where people are located. For HVAC systems, use the highest efficiency filters your system can handle (MERV 13 is ideal). 
  3. Provide respiratory protection for those who work indoors. At minimum, require face coverings, which provide source control and very limited personal protection against wildfire smoke and virus particles. 
  4. Monitor the Air Quality Index (AQI) in your area. 
    • When AQI is below 50, maintain outdoor air at maximum. 
    • When AQI is between 50 and 100, consider reducing outdoor air.
    • When AQI is over 100, reduce outdoor air and recirculate air indoors. Begin to reduce occupancy further if possible. During the pandemic employees should wear face coverings or N95/KN95 filtering facepieces indoors when building air is being recirculated and Oregon health agencies (OHA and Oregon OSHA) require or recommend this. 
  5. Support your employees in addition to your other business needs. This may include paid leave, different scheduling to accommodate remote work, and mental health support.

Additional considerations

Consider these routine measures to help improve indoor air quality during allergy and wildfire smoke season: 

  • Keep doors and windows closed. 
  • Make sure your HVAC system is operating properly. 
  • When renting or purchasing portable air cleaners with HEPA filters:
    • Check the clean air delivery rate (CADR) and select the device with the highest number. 
    • Do not use ionizing air filters that introduce ozone, which is a respiratory irritant. Review Air Cleaner Information for Consumers | California Air Resources Board to find a portable air cleaner. 
    • Position portable HEPA filter units away from doors, windows, and foot traffic, but far enough away from walls and corners that air can circulate around them. Follow manufacturer instructions for maintenance. 

For additional information, see our resources on wildfire smoke safety and controlling the spread of infectious diseases.