[riquito]

> CO2 levels are locally elevated in the area where you exhale.

That's the same area we inhale from... Wouldn't be right to measure there then? It's not like we're interested in the amount of CO2 on the ground (in this discussion)

[Aurornis]

No, because the studies that establish the levels correlated with cognitive changes use ambient CO2 levels. Not with a stream of air directed, maybe, from your nose to your wrist.

It is not possible to come up with a different baseline for wrist-worn monitors because the measurements could change significantly based on even small factors like the position of the wrist or smartphone.

[hansvm]

That makes sense to me. There's a causal link between ambient air CO2 levels and cognitive changes, but the air in front of your face, which you breathe, doesn't play a role...

A lack of direct study might make "in front of your face" numbers harder to interpret in absolutes, but relatively speaking I do think that's the number which matters more. Whole-room analysis is just a proxy for the air in front of your face.

[popalchemist]

Presumably after a month or so of being worn during the day and taken off at night (when the breathing doesn't apply -- and the device knows this), the device could deduce what the influence of the wearer is.

[jason1cho]

Exactly!

I installed a CO2 monitor at home, which reminds me of ventilation in winter when I keep windows closed and heating on.