> 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.

Not wrong, but it is perhaps worth noting that there are already standards for proper ventilation. Generally you're looking at 5–10 cfm/person (2.5-5 L/s), depending on the facility and purpose of the room; see Table 6.2.2.1 in ASHRAE Standard 62.1 for the US:

* https://www.ashrae.org/file%20library/technical%20resources/...

Maybe set up a monitor, but if the room/facility has recently been renovated and meets modern (>2013) building codes, this 'should' have already been taken into account.

Should…

Whenever I travel, I bring a CO2 meter with me. It’s amazing how often the air is bad. Often in unexpected places. My meter hit 3100 in an uber once. I didn’t even notice until I got to my hotel room and looked at the data log. It was a fresh, hot day outside. The uber had windows closed and AC on. I bet he had no idea - but he was driving with significant cognitive impairment. Takeoff and landing in planes are always the worst. If you get sleepy as the plane is taking off, it’s not you. The plane’s ventilation doesn’t work properly when the plane is stationary. So before a plane is in the air, they often hit 2500.

Building codes that address this are wonderful, however:

- Plenty of people live or work in older buildings, where are not up to standard. For example: my office probably violates the air quality sensibilities of the Victorian era, which is when it was originally built.

- Equipment breaks down, isn't operated properly, or wasn't installed correctly. Having monitors that measure air quality is an extra check. While you may not be able to get direct action upon a consumer sensor, it can help you push for action.

I've been in buildings of varying quality over the years. I've seen how it takes time to get people in to do air quality testing. Heck, I saw the government claim that the air quality was acceptable in schools during the pandemic because the schools had passive ventilation systems. That meant they could open windows. (To be fair, the air quality in most of those buildings was probably fine since that was how the buildings were designed. That said, such standards make it easy for some buildings to slip through the cracks.)

So yeah, sensors to the people!

I think modern domestic houses its the opposite. At least in Netherlands insulation is such a strong focus, due to climate change I think, that modern appartments have terrible ventilation

This is correct, but there's still a lot of opportunity to do better.

I've been involved with the build out of several office spaces in new and old buildings. We always took this sort of thing seriously and measured each room independently for a week (many at a time) ensuring we accounted for periods of high occupancy.

This let us tune the HVAC systems to operate more efficiently, ensuring comfortable temperatures and air circulation. Every time I've seen this done there were structural deficiencies that required remediation, some times it meant adjusting duct work.

Most modern office buildings are designed to be a platform for constructing spaces, as spaces usually evolve and change between leases and tenants. They're designed to accommodate this sort of thing.

However I've found that no build out nails this the first time. It's very hard! Often times things look fine but once you get people in the space things change drastically. It requires time and effort to address.

Several of my offices had such good air that I'd prefer being there over pretty much anywhere else -- even outside on poor AQI days.

I've also found that a lot of offices don't do any of this and their air quality is noticeably poor. And lastly I've found that the oldest buildings, including schools -- and I'm talking really old -- have very good air because they are so incredibly leaky. They're usually harder to cool and heat, though.