A/C AND Fresh Air
The covid-19 virus levels in most U.S. communities are low, as measured by the death rates and the levels of virus detected in sewage sampling. And nationally, the rates have been lower in every summer beginning with 2020, partly because people are spending more time outside in the milder weather. (Except Florida of course—sorry, folks.)
However, the rates have always bumped up a bit in August. Why? Because as more air conditioning is turned on, people close up all the windows to not waste the cool air. For buildings with proper fresh air ventilation as part of the air conditioning system, that’s no problem. But a lot of buildings have NO fresh air when the A/C is running, and this creates ideal conditions for the spread of covid-19 and other airborne diseases. Five times more diseases spread, according to one study. (See Dec. 16th, 2022 blog post.)
Plus, as readers of this blog know, good fresh air at the rates affirmed by the WHO and the CDC let our brains fire on all cylinders. (See Oct. 14th, 2022 blog post.)
So yes, it’s going to take a little more A/C and electricity, but if you want to give the people in your building optimum healthy air conditions, don’t hesitate to crack open some windows if that’s what it takes to have good fresh air levels (30 cfm per person, or CO2 readings below 800 ppm). If you don’t have a good CO2 meter (see Jan. 20th, 2022 blog post), you can sometimes tell by a slight odor that you notice when first entering a room when it’s shut up too tight.
Wildfire Smoke Protection
All well and good, but what if the “fresh” air is full of wildfire smoke? As you can tell from the discussion above, it’s not a good idea to hide inside buildings with no fresh air at all. Previously, we reported on using (expensive) HEPA filters in open windows to remove the smoke from the fresh air that people need. (See Jun. 8th, 2023 blog post.)
Now we have taken that idea further, and found that regular furnace filters work just fine for removing the smoke. The type of filter to get is MERV-13, also called FPR-10. Filters are available in all degrees of cost and performance. But the better the performance, the more the filter inhibits the full flow of air, so during the pandemic, it was found that for filter upgrades for HVAC systems, MERV-13/FPR-10 was the best compromise level. These filters are now readily available from good hardware stores, in a variety of sizes. You can get the best fit for your partially-open windows, or in some cases use oversized ones.
It turns out that these filters work well installed in windows, where the natural ventilation rate is very low, giving the filters the chance to do a good job removing the smoke particles. In a home test, here are some example readings of outside vs. inside (filtered) air quality. These are on the U.S. Air Quality Index scale where 0-50 is “grade A”, 50-100 is “grade B”, etc. on up to “grade F”.
Outside 154 - Inside 25
Outside 142 - Inside 50
Outside 158 - Inside 55
Outside 144 - Inside 33
Outside 127 - Inside 25
Not necessarily all the way to “grade A” but a big improvement!
And a final note, if you DO have filters (should be MERV-13) in your HVAC systems and you have been through a period with a lot of wildfire smoke, it’s time to check and probably replace the filters. Here’s an example from the internet (WLWT5) of before-and-after filters:
A "New” Mask
This is really great news—do you know there’s a special type of mask, readily available, that is perfect for filtering out the wildfire smoke if you need to be outside on a really "bad air day”? It’s been here all along, for working in smoky and dusty air, usually caused by what people are doing: sanding wood, cutting drywall, etc.
These are the same N95 masks that remove 95% of the small particles the size of the wildfire smoke, and used for covid-19, EXCEPT with the important addition of an “exhalation valve”. This means that your exhaled air is not filtered, but leaves the mask readily, so that your incoming breath is mostly cool, fresh air. VERY pleasant and healthy to wear compared to the valveless masks where you are rebreathing your warm, CO2-laden exhaled breath.
And, there are still many people who are taking covid-19 protections when around other people, due to compromised immune systems, other medical issues, or natural risk avoidance. These comfortable masks with valves are now OK to use for this purpose. Your unfiltered exhaled air is certainly no worse than the exhaled air from people not wearing masks, which of course is most people these days.
So try out these comfortable masks with valves! We haven’t yet picked a favorite model, but we will let you know when we do.
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