One surprising finding I'm having from taking CO2 readings in various places is that I'm consistently getting readings between 700 and 800 ppm at supermarkets.

I mostly took readings at peak hours. I'll need to go back at off peak times to see how much the readings change. I was really amazed at how "not terrible" the reading at Trader Joe's was.

Picture 1: Trader Joes at noon on a Saturday. It is packed. It was a total surprise to see CO2 readings between 700 and 800ppm! (Fair)

Picture 2: Smart and Final, a mostly California-bases grocery outlet selling a mix of regular groceries and bulk package items with a reading of 714ppm. (Good)

Picture 3: Walgreens Pharmacy, at off peak hours. 529ppm. This is very good, but hard to believe. I'll have to go take this again.

Picture 4: Nob Hill Foods, a small grocery chain in Northern California. 726ppm. Good-Fair.

#aranet4 #co2 #covid #traderjoe

I'm making some blunt assumptions about what these readings mean. From what I've been gathering from scientists posting about air quality readings, 400ppm is a baseline and every +200ppm gets you from excellent to good to fair to unhealthy.

Most people seem to be suggesting 800 and below as the line to really start exercising more strict caution if you're trying to avoid infection.

But keep in mind that's based on 400ppm as the baseline. My baseline for some of these readings is shown in the attached photo. It's 470ppm outdoors on that day.

My baseline is likely higher because I'm in an urban area at a mall near very busy roads. There's a lot of extra ambient CO2 so my cutoff lines would be 670 and below (excellent), 870 and below (good), 1070 and below (fair).

Every 400ppm above baseline roughly equates to 1% of the air you breathe being exhaled by someone else. That's like getting mouth to mouth once every 6-8 mins.

#aranet4 #co2 #covid

@BruceMirken you're right. All things are relative here. What we have here are degrees of risk, not degrees of safety.

The reason why I'm asking people who got stuck on conceptualizing risk in social distancing terms to drop it is not because all risks are equal.

The person right in your face is definitely a more potent risk, but if we're playing just the numbers game, only a handful of people can be in your face, but hundreds of people can be close enough to infect you if the air quality is poor. Yet people mostly look at what's in front of them.

Even during heavy spikes in 2020, in most places, at any given time there were fewer than 1 out of every 100 people who were likely to be highly contagious. Chances of being face to face with that 1 in 100? Small, especially if the symptomatic ones self quarantine or try not to get too close to anyone. Chance of ending up in the same room? Quite high.

That's the point here and some people who are trying to balance risk with reward need to understand that.