CPCSupport:New Pandemic Protocols

You may have seen some people carrying around CO2 detectors to determine how safe their air is. Liesl McConchie has been a big advocate for CO2 management in schools, where, by in large, no one wears a respirator, so any improvement to HVAC systems, ventilation, and filtration is welcome improvement over nothing at all. It has also been helpful for microbloggers to document the crappy HVAC systems across our built environment. After all, no one likes air pollution.

The theory is:

• People always breathe things out.
• People always breathe out more CO2 than is taken in.
• If people are infected with an airborne pathogen, they will always breathe out new pathogens.
• If a pathogen exists, it has a chance of being breathed in and a chance of infecting a person.
• If no people exist, there are no pathogens and no change to CO2.
• Therefore, CO2 levels are correlated with pathogens. QED

Add in that pathogens degrade outside, maybe correlate it with cognitive ability at certain CO2 levels, and voila: a CO2 safety chart:

CO2 Level	Safe?
1500+ ppm	Danger!!
800-1500 ppm	Caution!
500-800 ppm	Good
500 and below ppm	Great!

You may have spotted a few problems here. Aside from the improbable, like an tank of [insert gaseous compound here] bursting and displacing all the CO2 in a room, and more practical concerns, like stale air in semi-confined spaces or rooms with aggressive non-ventilation controls not correlating with danger...

(Or just being right next to a person that's infected... but I hope you've spotted the bigger problem)

It still hasn't stopped some people from using CO2 monitors to decide when to wear a mask or not. You get the benefits of avoiding COVID while also avoiding much of the social inconvenience of wearing a mask! What could possibly be the harm in that?

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Enter this paper , published in Nature. Assuming it's properly done, it details the probability of getting infected with COVID by CO2 level. Well, great! So far our theory is holding up.

Omicron is more infectious than older COVID variants, okay...

Greater CO2 is correlated with likelihood of infection, so: at what point are CO2 levels dangerous?

800+ ppm.

Lower levels are also have a pretty high likelihood of infection, given the large error bars...

But does it even keep rising as CO2 reaches 2000, 3000 ppm?

Not really...

I think we're in trouble. Let's redo our safety chart based on this paper's findings:

CO2 Level	Safe?
800+ ppm	Dangerous!
500-800 ppm	Likely dangerous
500 and below ppm	Barely adequate method of suppressing COVID infections

Oh yeah, this is for Delta too. The difference between 500 ppm and 800 ppm for Omicron is worse, and the authors didn't even bother charting the other higher levels of CO2 for any of the other variants.

But wait, it gets worse...

If you look at figure 2, you'll note that at 3000 ppm, the rate of viral decay is significantly slowed. So everyone could the leave the room for hours in this situation and still encounter viable virus. And the author of the paper has noted in a YouTube video that it actually plateaus, so good luck having the air clean itself naturally in a reasonable timeframe.

So great, let's update this table again:

CO2 Level	Safe?
3000+ ppm	Bordering on insanity!
800+ ppm	Dangerous!
500-800 ppm	Likely dangerous
500 and below ppm	Barely adequate method of suppressing COVID infections

Conclusion

While CO2 monitors are a useful tool for determining if HVAC upgrades or air purifiers are needed, it isn't enough to stay safe from infection, especially with the speed at which COVID evolves.

Needless to say, you're still going to need your respirator for a while, at least until far-UVC bulbs become building infrastructure, which can allegedly reach up to 184 equivalent air changes per hour. By contrast, Lisel's efforts in schools have only reached 10 ACH at most, and the CDC only requires a paltry 5.

So yeah, it's that bad. We're only 2% in the place where we should be with a rapidly evolving pathogen, 4% if you're lucky. A 100% improvement doesn't sound so amazing after all...