Returning to college teaching mid-pandemic, I bought an SAF Aranet4 Home CO2 meter for measuring my classrooms. It mostly lives in my apartment, waiting to alert me in case I didn't realized I was using my gas range.
There's good evidence predating the pandemic that sufficient air exchange can nearly eliminate respiratory disease transmission. Just as they learned long ago in London that one could eliminate cholera by not drinking sewage water, we understand that the air quality and rate of exchange of indoor air should approximate that of outdoor air. We're however too cheap to do anything about this; it will take more deadly pandemics to drive the needed infrastructure changes.
Do you wince at the idea of people in London drinking sewage water? Those ignorant savages? Yeah, that's how people in the future will look back at us, getting colds and worse all the time in indoor air cesspools.
As we breath out CO2, it makes a great way to measure whether we're changing the air in a room fast enough to keep up with occupant breathing. Wilderness air passed 400ppm as part of global warming. My Manhattan apartment is above the Henry Hudson Parkway, and I can tell the time of day and day of week from the effect of traffic on my CO2 meter. I'm lucky to ever get below 450ppm.
The Aranet works far better than a $30 meter at the measurements a $30 meter will make, such as humidity. By appearance and build quality it's in a different league. CO2 is a bonus.
When I can, I run a pair of box fans exhausting through the windows in one room, letting the air in through the windows in the other room. This feels roughly like living on a houseboat, and is how I can read 450ppm.
I'm now at 728ppm after cooking lunch, windows closed. There's a good kitchen exhaust to a roof fan, so I can get that number down a fair ways by cracking a window.
Showering for fifteen minutes in my last apartment would push the bathroom CO2 up to 2000ppm, even with the stock weak exhaust fan on, and it would drop slowly for twelve to fifteen hours but never below 1200ppm so long as someone was home. 750 sounds like luxury :)
I live an hour drive north of New York City in a small, rural town of about 2,000 people. Large lot sizes, not much going on pollution wise. The lowest my CO2 has been so far is 659. This is when I open the windows for 30 minutes. I haven’t tried anything more aggressive than that. Either our rural, small-town air is worse than NYC for some reason, or the NYC air isn’t that bad? Very interesting.
Try opening your window for an entire day (e.g. when you're away) and see the result. If it's still above 600, my guess is that the sensor is crappy. Also, apparently some sensors recalibrate themselves against the lowest level they've seen in the past X days - so ventilating heavily may recalibrate it.
There's good evidence predating the pandemic that sufficient air exchange can nearly eliminate respiratory disease transmission. Just as they learned long ago in London that one could eliminate cholera by not drinking sewage water, we understand that the air quality and rate of exchange of indoor air should approximate that of outdoor air. We're however too cheap to do anything about this; it will take more deadly pandemics to drive the needed infrastructure changes.
Do you wince at the idea of people in London drinking sewage water? Those ignorant savages? Yeah, that's how people in the future will look back at us, getting colds and worse all the time in indoor air cesspools.
As we breath out CO2, it makes a great way to measure whether we're changing the air in a room fast enough to keep up with occupant breathing. Wilderness air passed 400ppm as part of global warming. My Manhattan apartment is above the Henry Hudson Parkway, and I can tell the time of day and day of week from the effect of traffic on my CO2 meter. I'm lucky to ever get below 450ppm.
The Aranet works far better than a $30 meter at the measurements a $30 meter will make, such as humidity. By appearance and build quality it's in a different league. CO2 is a bonus.