Among the probably most important and universally relevant measurements offered by air quality monitors is carbon dioxide/monoxide. Humans are not really built for realising when these are elevated, other than feeling sleepy and generally experiencing reduced mental capacity, which by its self-referential nature is not conducive to understanding that you are experiencing reduced mental capacity or being motivated to take measures about it (such as opening windows).
These are all of the ways in which air monitoring information is actionable for me:
— Excessive carbon dioxide: as mentioned, it’s a call to open windows and possibly doors, depending on wind direction and window/door configuration in the flat and the building. It can reach surprising, and in my case unsafe by at least one country’s standards, levels overnight if your flat has decent insulation and little airflow. Besides, it just feels nice to have more oxygen knocking about your internals.
— Excessive (which should really mean non-zero, but in today’s ecology let’s say “elevated”) PM2.5 means I should close windows (usually this pollution comes from outside) and ramp up air filtering, and potentially postpone exercise while particulate matter is too high. I have a separate cheap air filter but lately it turned out that a Mitsubishi dehumidifier does a great job at this—which, by the way, I have realized only thanks to an air monitor.
— If both carbon dioxide and particulate matter are high, I’d most likely open the windows first to lower the former then close the windows and run air filtering while hanging out at the office or having a walk (potentially with an N95 mask on if it’s really bad outside).
— VOC, which often originate from chemicals used in furniture or flooring, if your monitor measures those, could probably be addressed by adding activated carbon layer to your air filter (and by opening windows). I think they are filtered slowly and this might take months, but my monitor did not measure VOCs so I don’t have first-hand experience. An air quality monitor could help you understand whether you are wrong or right in thinking your new floor made your air full of VOCs when all you can go by otherwise is just a vague chemical smell.
— Elevated background radiation means you should probably just move, usually it is building materials or something not easily removable anyway.
I would say that with these numbers available there is a danger you’d stress over and min/max them. It’s probably better to just use the measurements to understand the patterns and see if something is really out of ordinary or elevated for prolonged periods of time. I did that first (and did not expect to see how quickly carbon dioxide builds up, how quickly everything deteriorates with any cooking, including when done by a neighbour if I open windows and the wind blows the wrong way, the speed with which outside pollution permeates the indoor space, how effective my air filtering is, etc.), now my air monitor is broken and I am not overly concerned until I have to move to a new place.