Furnace Filters and Air Purifiers: Powerful Tools for Reducing the Risk of COVID-19

 During the past week, I have gotten a number of emails asking about the weather on Thanksgiving Day. 

 Why?  Because a number of folks are planning on having their holiday meal outside in their garage, with the door open, to lessen the risk of COVID-19 transmission.


And it is true: a comprehensive search of the medical literature suggests little evidence of outdoor transmission.  COVID-19 spread is predominantly a problem in indoor spaces with poor ventilation, particularly when large number of people stay in such spaces for a sustained period of time.  

COVID-19 particle concentration levels are critical--lowering the concentrations can greatly reduce the risk and the severity of the disease if you get it.  Outside, there is a huge amount of dispersion of particles, so concentration are inevitably low.

So enjoying your meal in a garage with open doors greatly lessens the risk of COVID-19, no doubt about it.  And the latest forecasts suggest western Washington will have a dry Thanksgiving Day with no rain in the lowlands, light winds, and seasonal temperatures (upper 40s).  

Wear a sweater and cap, and add a heat lamp or radiant heat, and it might be ok.  Some warm cider or a hot toddy might make it better than that.

But for those folks who want to avoid moving to the garage, there is a powerful tool you can use to reduce the potential for COVID-19 transmission:  filtration of the air with top of the line furnace filters or a high quality air purifier system.

I know a bit about this approach because of the recent wildfires and their resultant smoke.  And the Centers for Disease Control (CDC) and the EPA acknowledge the value of air filtration for COVID as well.

The bottom line:  a good furnace filter or air purifier system should be able to greatly reduce the numbers of COVID-19 aerosols in the air you breath indoors (if there are any, of course).

COVID-19 Particle Sizes

The COVID-19 virus is about .1 micron in size (a micron is a millionth of a meter).  But the virus generally is enveloped in small aerosol droplet produced when we exhale or cough, ranging from .3-1 microns for the smallest to 3-10 microns for larger ones.

It turns out the high quality furnace filters can very effectively remove particles in these size ranges:  filters that are known as MERV 13 or FPR 10 (or better).

This summer, one of my UW colleagues and hiking buddy, Professor Dan Jaffe, tested the ability of a furnace filter to clean the air in a single room.   He created a very inexpensive filtration system, taping a MERV 13 furnace filter to a box fan (total cost about $40).   

There were a lot of particles in the air from the regional fires, so this was serious test!  Below are the results showing the how the concentrations of particles of .3  and 2.5 microns changed in time.  Just amazing... most the particles were taken out in 15 minutes.  It would do the same for COVID-19 aerosols.  A number of other groups have done similar tests with the same results.

Some of you might have constructed such a box fan filter during the wildfire smoke period, while others may have purchased a commercial air purifier.   If you have forced air heat in your home or apartment, make sure that it has a MERV 13/FPR 10 filter in place, and set the fan to run continuously.

This was proven to work very well for wildfire smoke (whose size is similar to small COVID-19 droplets)

Image courtesy of Dan Jaffe

If you have a fireplace in your home or apartment, use it, and open up a window.  The fireplace will suck in lots of outside air and warm you up to compensate.  More outside air will help reduce COVID-19 aerosol concentration.

This kind of air filtration will not necessarily eliminate any COVID risk, but is one approach to lessening airborne transmission. Enjoy your holiday meal.

Addendum:

The Wall Street Journal has put out a excellent video on ventilation and filtration for COVID-19:

https://www.wsj.com/video/ventilation-is-key-to-battling-covid-heres-why/EC6274D1-B4F0-40DF-A8EC-F9BDA7C5D1A1.html?mod=trending_now_video_pos1

________________________________________

My latest podcast on Thanksgiving week weather and major NW storms:

Click the play button to listen or use your favorite streaming service

Or stream my podcast from your favorite services:

Would you like to support the podcast? 
If so, click the Patreon box below. 












Comments

Post a Comment

Popular posts from this blog

The Time of Year You Can See the Air Move

Image
  Most of the time, you can not see the air move.   You can feel it, but the complex, turbulent motions are invisible to you, except when it interacts with leaves and branches on trees and plants. But for a few weeks of the year, the sky is full of small, cotton-like tuffs that like a natural MRI machine reveals the complex three-dimensional motions of the atmosphere.   Cottonwood season.  And we right in the middle of it.   Being cottonwood aware is of particular value this year.  It reveals the active dispersion and movement of air that makes the outdoors essentially COVID safe, and thus should be of some comfort for those nervous about transmission outside. Cottonwood seeds are embedded in small cotton-like fibers.   A million seeds weigh about 3 pounds.  Yes, each seed and tuff weights about .000003 pounds.   And that fact, plus the cottonwood tuff, means that these seeds fall VERY, VERY, VERY slowly.   So slowly that they are excellent markers for the three-dimensional flow of the
Read more

Why so little lightning in the Pacific Northwest? And a very nice weekend ahead.

Image
During the past 24-hours, there have been a few lightning strokes over the region (see below) but nothing to write home about (see below). It turns out that the Pacific Northwest and the remainder of the West Coast have some of the lowest frequencies of thunderstorms in the entire country (see below). But why?    My podcast provides the answer. And I also give the weekend forecast....and I think most will like what I have to say. To listen to my podcast, use the link below or access it through your favorite podcast service. Some major podcast servers:     Like the podcast? Support on Patreon 
Read more

Strong Atmosphere River Heads into British Columbia and Southeast Alaska

Image
While the Northwest has been drier than normal, it has been drenching wet a few hundred miles to the north. An unusually strong atmospheric river ....a long current of moisture stretching southward to the subtropics...has been in place for days, bringing large amounts of water vapor to Alaska.   And the atmospheric river will be in place for several more days, slowly moving southward. To illustrate, the scale and beauty of the atmospheric river, here is a water vapor satellite image for 11 AM today. The lighter areas have more water vapor.  You can see the current of moisture extending from near Hawaii into central BC.  This current is the result of low pressure over the Gulf of Alaska and high pressure offshore of California.   A forecast of total water vapor content in the atmosphere for 11 PM tonight shows a healthy atmospheric river (white and blue colors indicate the higher amounts of moisture). As this atmospheric river slams into the mountainous West Coast, the air is forced to
Read more