> 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.