Website for Nathan Moore, Physics, Winona State University
A Corsi-Rosenthal air filter is easy to build. Buy four MERV 13 furnace filters, a box fan and some masking tape. Using the fan’s cardboard packing, create a cube with a solid cardboard bottom, filters on the sides and a fan on top. Direct the fan blowing upward, so it pulls air through the filters on the side of the box. Seal the edges with masking tape and plug it in. You now have an air filter that’s roughly equivalent to the HEPA filters they use in surgical operating suites.
These box filters first became popular during the early days of COVID, when air filtration of small droplets seemed like a good idea. I built a few then, for my classroom, lab and my wife’s second-graders. I still have one downstairs in our house, as a device that filters COVID-bearing droplets is also remarkably effective at filtering out smoke when I load our wood stove wrong and it backdrafts.
What does this have to do with the future of Minnesota? Climate change is certainly here, and warmer, drier weather patterns are leading to more frequent forest fires in the parts of North America that are upwind of us (“Ashen gloom, record bad air,” front page, June 15). Unlike the methylmercury in walleye from coal-burning power plants, there’s no way to opt out of breathing, and everyone in Minnesota will need to either figure out how to mitigate this health risk or suffer the health consequences.
Is wood smoke really that bad? Yes. Richard and Elizabeth Muller wrote a short memo that compared deaths from smoking cigarettes to death from air pollution (in China). In brief, the worst sort of air pollution is particles 2.5 microns or smaller — small enough to move directly into your blood stream — which are linked to many cardiovascular and respiratory problems. Roughly speaking, every 22 μg/m^3 of PM2.5 concentration in the air is equivalent to smoking one cigarette. At 7 p.m. on June 14, the PM2.5 level was about 220 μg/m^3 in St. Paul. If you breathe that air for a day, it’s equivalent to smoking about 10 cigarettes.
What kind of future are we going to have in Minnesota? One where we each must take responsibility for mitigating climate change in our literal backyards and living rooms? One where the Legislature (and the feds) do little to keep the situation from getting even worse?
Nathan Moore, Winona, Minn.
The writer is a physics professor.
A similar letter was published by the local Winona papers
The air quality in Winona — and the Midwest generally — has been really bad lately. The “chewiness” of the air can be measured by the concentration of particles that are 2.5 micrometers or smaller.
PM 2.5 particles from wildfire smoke upwind of Winona are small enough to go deep into your lungs and straight into your bloodstream. I’m not a doctor, but I’ve read that PM 2.5 exposure is linked to increased heart attack and lung disease risk. How much risk? Breathing PM 2.5 smoke at a level of 22 micrograms per cubic meter all day is equivalent in risk to smoking one cigarette. The air in Winona on Wednesday morning was at a PM 2.5 level of 158 micrograms per cubic meter, or 7 cigarettes if you’re outside enjoying the hazy weather.
What can you do to mitigate this risk? First, be aware of the PM 2.5 level. Winona State University has a PurpleAir PM 2.5 sensor that continually broadcasts data to an online air quality map at map.purpleair.com. This map is based on community-sourced measurements, and the U.S. EPA uses these measurements in their online fire and smoke map at fire.airnow.gov.
Second, filters help to reduce the PM 2.5 level. An N95 mask when you’re outside and a $60 corsi-rosenthal fan cube in your living room can dramatically improve the quality of the air you’re breathing.
Nathan Moore
Winona
This also showed up in The Physics Teacher