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Turn up the HVAC v. COVID-19

April 8, 2020

All essential services need to take actions to move, filter, and avoid contaminated air.

Turn up the HVAC to reduce the risk of coronavirus infection.

Open doors, open windows, use fans, and be careful of where people are or have been breathing.

People who have the virus breathe it out in clouds of microparticles – blow those particles away, filter them out, destroy them with heat, and stay away from breath clouds – anything helps reduce the risk.

  • Open the doors and windows if you can. Microparticles will disperse faster (see this video).
  • Increase HVAC fan speed and percent of outside air coming  – heat may also help.
  • Blowing air with a fan should be helpful (be careful of direction)
  • Add a HEPA filter if you can (HEPA will filter particles much smaller than the virus).

Any kind of air movement should help disperse concentrations of particles and make them agglomerate into larger particles faster. Larger particles are more likely to fall out of the air and less likely to reach the deep lung when we breathe them in.

Stay out of others’ breath clouds as much as possible. Especially if either of you are breathing hard. Example: you’re walking down the sidewalk, someone runs past you, breathing hard – they are leaving a trail of breath cloud. Don’t let a mask give you a false sense of security. Step out of and avoid that trail of breathcloud.

Masks help in both directions but have only limited effectiveness.

Even N95 masks when worn correctly only reduce the risk by about two-thirds versus normal breathing, one-half versus surgical masks (according to one large study of airborne transmission of flu virus to medical personnel). You may eliminate the protective effect and may even increase risk with heavy breathing and/or mouth breathing. The masks were not designed for athletics.

Nose breathing is less dangerous than mouth breathing – the nose and nasal passages make a natural filter which helps limit the reach of small particles.

Get this information to your local grocery stores and markets and hospitals – help protect people vulnerable on the front lines.


The public has not been adequately warned about the risk of airborne transmission and how to best reduce risk, which should have started months ago and may have been able to greatly limit the pandemic.

This article to be updated with more of the scientific basis.

#COVID19 #microparticles #coronavirus

Photo source:

Meggs holds a Master’s in Public Health (Environmental Health Sciences Division) from the University of California at Berkeley.

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