The problem is there are a lot of effectively 'fake' CO2 monitors. They can't monitor CO2, they only monitor something else and work backwards to estimate CO2 levels.

The cheapest real ones I've found are on the order of ~$150

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buckle8017 3 days ago | parent [-]

Unless your CO2 monitor has purge gas to calibrate it's going to underestimate indoor CO2.

They all assume that they will be exposed to atmospheric concentrations of CO2 at least once a week.

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imp0cat 3 days ago | parent [-]

In their defense, they usually mention this requirement in the manual.

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buckle8017 3 days ago | parent [-]

Sure but do you take your CO2 meter for a walk?

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crazygringo 3 days ago | parent | next [-]

When nobody is home so there's no CO2 being emitted, it goes down to outdoor levels within a couple of hours if your windows are open even a crack.

If you have a meter that shows you a graph on your phone, you can watch it reach equilibrium. It's very obvious.

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Etheryte 3 days ago | parent | prev [-]

And in similar vein, when was the last time you read the manual for a household appliance?

	▲	imp0cat a day ago \| parent [-]
		Both fair points. I like to familiarize myself with any appliance I buy, so I tend to read the manual at least once. And yes, it's usually a waste of time. :)