One interesting effect of the pandemic is that I'm hyper-aware of the quality of indoor ventilation. With case counts rising again even in heavily vaccinated places, I'm annoyed that we haven't done more with air filtration, and... I'm not even sure why?
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Like many other viruses, COVID spreads primarily through aerosolized respiratory droplets, which are small enough to hang in the air for a long time. But, they are large enough that a normal HEPA air filter can remove them.
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(For a summary of the history of aerosols in the context of COVID, I really like this thread: twitter.com/jljcolorado/st)
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1/ TIME FOR SOME AIRBORNE + DROPLET HISTORY
Now that @WHO and @CDCgov have finally accepted *after a year of denial and delays* that airborne transmission is a major mode for COVID-19, it is time to review the history to try to understand why this response was so poor.
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Air filters are really good appliances! I have one to help with dust and it's cheap and quiet. They're basically zero effort once they're set up, unlike masks or shutting down businesses. Lots of people out west already have them for smoke season.
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The wonderful estimates that a HEPA air filter with a high enough flow rate reduces COVID transmission risk by 3-6x, with longer (more dangerous) interactions getting the greater factor. That's comparable to having everyone wear a cloth mask (!!!)
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Air filters are a great complement to vaccines, since they filter particles regardless of what virus or variant lives on them! I wonder what the effect of this on flu or cold virus transmission would be. This might be worth it even for the post-COVID benefits alone.
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Despite this, I have heard very little about ventilation/filtration upgrades in offices or retail stores. Anecdotally, I've only noticed public air filters in a One Medical office (good job!)
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I have no idea how much commercial HVAC upgrades would cost, but as a lower bound: we could buy the same air filter that I have for dust control at home (~$400 MSRP for 350 cfm CADR) to cover all 97 billion commercial sq ft of real estate in the US for ~$110 billion.
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(Assumptions: retail prices of $400 per 350 cubic feet per minute of air flow, 97 billion sq ft of commercial real estate based on a random figure I found online, 12 ft average ceiling height to determine air volume, microCOVID goal of 5 air changes per hour.)
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Obviously, $110 billion is a lot! But... not that much on the scale of the trillions of dollars spent on COVID relief. I'd also expect that you could do a lot better than paying retail prices at country-sized volumes.
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The weirdest part is that I don't understand why this hasn't happened more? It's useful on the margin and doesn't require much coordination. As far as I know there are no regulatory barriers. I would preferably patronize businesses that advertised good ventilation or filtration!
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The best explanation I can think of is that good ventilation is illegible: unlike masks, it's hard for an individual to verify that an area is well-ventilated or well-filtered.
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Apparently Belgium has mandated CO2 meters in many public spaces (restaurants, bars, gyms), using CO2 as a proxy for fresh air ventilation (that is, air brought from outside). Filtration won't affect that, but it seems like a pretty good attempt at making ventilation legible.
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(Source for claims about Belgium, from what appears to be the government's official COVID info site: info-coronavirus.be/en/ventilation/)
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Either I'm missing something (and please tell me if you think I am!), or we're... just collectively making a terrible decision for no good reason? We're trapped in a bad state, and it's not even like we need coordinated action to make it much better. Any ideas?
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(I've not verified this in any way) Apparently teachers are trying to use air filters in their classrooms and getting told that they are... fire hazards? A large air filter draws maybe a few hundreds Watts.
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Replying to @j_g_allen
Fire codes- our district told us we couldn’t use them (we bought them for ourselves) because they’re a fire hazard.
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I wonder if this is an actual safety concern (albeit probably not one that outweight the benefit) a bureaucratic mixup, or someone on a power (ha!) trip.
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