Or you are just used to poor air quality so you don’t even notice it anymore.
and the fact that air quality usually gradually worsens over time. i think it's easier to tell bad air quality when you move in between rooms/spaces.
but i agree with the op that 'looking' at a display already subconsciously tells you something about the air quality and your relation to it. my air quality sensor [0] has a green/orange/red light system though, so i can sometimes just tell that the air quality is bad by a red led flaring up in the corner of my eye.
[0] https://www.tfa-dostmann.de/en/product/co2-monitor-airco2ntr...
previous discussion on the above meter: https://news.ycombinator.com/item?id=22764603
The AIRCO2NTROL MINI is a great little device to have in a bedroom or living room, the green/orange/led lights are easy to understand (think traffic lights) even by non-technical people.
I was referring to looking at a display to be timely informed about an event, crossing the threshold out of acceptable air quality, that can occur at any time of the day. If air quality is consistently bad you don’t need a measuring device but a good air filter. If instead it is not then relying on constantly looking at it is a poor solution.