[hedora]

I'm reasonably certain I notice levels above 800ppm. It's subtle, but everyone in the house starts getting a little edgy (kids and adults). Sure enough, the CO2 meter is reporting > 800.

I doubt I could differentiate between 800 and 1600 though.

[foobarbecue]

I'm not saying you're wrong, but remember 1600 ppm is only 0.16%, so that's impressive sensitivity. 4x atmospheric.

We've been discussing 1% to 3%, which is 10,000 to 30,000ppm.