What if someone uses a library CO2 meter and discovers that the library's ventilation is not very good?

Now that you know this, you can fix it! You can improve ventilation (which will reduce the CO2 ppm readings) or add filtration (which won't affect the CO2 ppm readings, but will make the air safer).

What if someone loses or damages a CO2 monitor?

Libraries expect a certain rate of lost/damaged materials and have policies for that situation.

Is good indoor air quality a substitute for wearing masks/respirators, or vaccination, or social distancing?

No. The Swiss Cheese Model of risk reduction reminds us that ventilation and filtration are good by themselves, but even better when combined with other "slices" of cheese.

Is it useful to lend someone a CO2 monitor for 1-2 weeks and then expect it to be returned?

Yes. CO2 monitoring is not like a smoke alarm or a carbon monoxide alarm, which need to be permanent. With CO2 monitors, on the other hand, you might take some readings, implement a ventilation improvement (like changing a mechanical system from "auto" to "on), and take some more readings to confirm that the system is working.

What's the difference between carbon dioxide and carbon monoxide?

Carbon monoxide is a colorless, odorless gas produced by incomplete combustion. It is dangerous, sometimes deadly.

Carbon dioxide is also a colorless, odorless gas, but it's not dangerous like carbon monoxide. Carbon dioxide is exhaled by people, so the difference between CO2 ppm in an indoor space and CO2 ppm in outdoor air reflects how much of the indoor air has been exhaled by people and might contain small viral particles.

Are any other libraries lending CO2 monitors?

Some libraries have been lending CO2 monitors, or indoor air quality sensors that measure CO2 as well as other variables, as part of tool libraries oriented towards energy efficiency and citizen science. Lending CO2 monitors with information about indoor air quality with respect to COVID-19 transmission is pretty new; click through to our media page to see some libraries that are already doing this.