[Aurornis]

> I really wish a Apple or another major OEM would integrate CO2 monitor into watches or smartphones

CO2 levels are locally elevated in the area where you exhale. Someone sitting at a desk with their hands on a keyboard exhaling through their nose would be producing a directed stream of elevated CO2 straight at the sensor on their wrist. Same thing if someone puts their phone on their desk.

Even with the IKEA and other cheap sensors that are becoming popular, there is a learning curve where users discover that putting it on their desk right in front of where they’re breathing produces higher numbers than having it even 5 feet away.

The false positives from having a CO2 sensor that close to everyone’s face would be causing unnecessary alarm all over.

> There are so many rooms, classrooms, movie theaters and other places with poor ventilation where you just feel dizzy, or fall asleep, not knowing it was just due to lower oxygen levels in your blood. Raising awareness is the only real solution.

If someone is falling asleep in this many different places I would suspect undiagnosed sleep apnea or another condition first and foremost. Spaces like movie theaters have very high volumes of air due to their size and commercial building HVAC has much higher standards for air circulation than even your home. If someone was falling asleep in so many different places then the most likely common theme is that person and it should be checked out!

This is another reason why putting CO2 sensors on everyone’s wrists would be a mistake: It would start getting blamed for every vague condition people experience. This has already happened with wrist-worn heart rate monitors. My friends in the medical field see people all the time who come in with vague complaints and they’ve self diagnosed as being related to their heart because they can see their heart rate now.

You also have the wrong idea about what elevated CO2 does. It doesn’t reduce the oxygen levels in your blood. It makes it more difficult for your body to expel CO2, which can produce subtle changes in many processes.

[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.

[cotwo]

The air infront of you IS the air you breed in, why shouldn’t it be measured?

[Aurornis]

Because the thresholds everyone gets from the studies were not measured in that location.

It would be like the weather station telling you it was 160 degrees outside because they put their thermal sensor on the asphalt, but you wanted to know the air temperature.

[BobaFloutist]

Or your watch telling you the room is 98 degrees because it's only ever measuring your body temperature

[Aurornis]

That’s a much better example. Thanks

[mito88]

98F = 36.6C

[tzs]

Wouldn’t it still be useful because you could look at changes in the measurement? E.g. if I can’t draw any conclusions when my phone says 800 at the start of a meeting because it might be where I’m breathing, but an hour later in the same place it says 2500 couldn’t I conclude we need to take a break and let the room air out?

[Melatonic]

Mostly agreed but with that much data couldn't we easily have an adjusted CO2 number for local sensors ?

I would imagine it's still relative unlike temperature on the wrist (which is too affected by body temp)

[avazhi]

CO2 does not stream out when you exhale like a fluid. It’s a gas. It dissipates quite immediately and behaves as all gases do - it expands to fill its container via something like Brownian Motion.

[Aurornis]

Dissipation does not happen instantly.

I’ve done development on products with CO2 sensors and I’ve spent a lot of time with them on my desk right in front of me and also off to the side. Readings right in front of me are predictably higher.

You can breathe into a CO2 sensor 18 inches from your mouth and watch the values spike upward.

[avazhi]

I generally have fans around, but I too use a CO2 detector in my home and have tested it in various places and situations. CO2 concentrations are not as localised as you are making them out to be. If they are elevated in front of my face, for example, I can also similar numbers just above and slightly behind my head. If you go outside and do it, you’ll be surprised that the number doesn’t move really change at all when at arms’ length. Airflow is really everything here.

And, spoiler alert: if the entire area in front of you has an increased CO2 concentration, then your environment has an increased CO2 concentration. That’s the entire point.

Suffice to say I disagree strongly with both the argument that this would lead to hugely erroneous readings and also with the notion that people would panic.

[Aurornis]

> And, spoiler alert: if the entire area in front of you has an increased CO2 concentration, then your environment has an increased CO2 concentration. That’s the entire point.

I don’t think you’re reading the discussion: The CO2 thresholds that people use are based upon ambient air.

The closer the measurement to your mouth, the higher the reading will be. It should be apparent why putting the sensor directly in front of your mouth will register higher numbers than having it across the room.

CO2 does not instantly diffuse throughout a space. If it did, it would be sufficient to have only very small air leakage in a space for the CO2 to diffuse out of it very rapidly

[fc417fc802]

Actually what you exhale is a fluid.

The CO2 content is a single chemical species within a mixed gas. Any air currents will cause mixing. Otherwise it undergoes diffusion which is actually a fairly slow process, although much faster in gases than in liquids.