Thread by @mikechenwriter

So at #StarWarsCelebration, I kept my Aranet4 CO2 meter with me EVERYWHERE. Granted, I spent most of the con outside, but for folks who gobble up data, here's what CO2 was like at a massive con to quantify COVID risk.

A brief primer: CO2 meters measure human exhalation in a space. Outdoors is about 425. The higher the number, the more % of other people's breath you're breathing in. That's a problem with an airborne virus.

In general, you want under 700 for indoors (this is building code). Under 1000 is where you'll want to be careful. Anything above that is an issue.

HEPA filtration does NOT remove CO2. But when you hit above 700, you'll want HEPA filtration to clean the air from exhalation. (I used a personal HEPA at the con)

This is why board/taxi is a huge issue on flights but NOT the actual flight when HEPAs run.

Okay, so here's a rough sense of CO2 at various things from the con:

Underground entrance: This was a BAD idea and the only time I took this way in. It hit 1500 for a few minutes, but as people shuffled in, it gradually dropped to 1300.

General con floor, open areas: The convention center was generally well ventilated with open areas hitting 600-700.

At my PRH signing, it was about 800-900 for the hour. Not bad considering a heavy traffic area and people waiting in line. You can see here it was 895.

At my MG signing (inside the store): Much less dense here and it showed, measuring mid-700s most of the time.

I didn't take a photo there, so enjoy my I DON'T LIKE SAND checklist shirt.

In line for an autograph: Dense crowd, moving slowly. Still was around 900-1000, which wasn't great but made sense. I held my HEPA up the entire time.

(There was a scheduling snafu so I left the line for my panel, but here's Sam Witwer signing the FACPOV story he narrated)

Note that if you took this same line and put it in a space with no active HVAC system, it would be much worse -- that's why planes hit 2k-3k regularly.

Backstage at Twin Suns: Hardly anyone here + tall ceilings = building standard of low 700s.

Also, it was very dark.

So in general, the actual facility had pretty decent ventilation! Anecdotally, most I know who tested positive pinpoint it to an external event/hangout, and this lines up.

I hope this helps some learn about systemic mitigations to minimize COVID! An open window makes a big difference, and HEPA filtration can be a cheap game changer (look up Corsi-Rosenthal box for DIY model).

For more #COVIDisAirborne, see this thread.

Also, huge thank you to @m_scribe @maiamajumder and @angie_rasmussen for answering all of my testing/symptom texts during the con and my post-con quarantine. You all deserve medals for your pandemic work!

PS This is another good thread on how ventilation upgrades can fundamentally change public health in both the near-term and far-term.