Yes...formaldehyde exposure is a big issue in the US. Not many know of it. I bought a new construction house, so it has new carpet, paint, cabinets, wood flooring etc has an off gas effect. I honestly it's criminal to allow builders to build like this, or material to be manufactured like this. That "new car" smell, that smell when you open up new furniture made of plywood (the glue contains formaldehyde) .

There are threshold laws in the US and Europe. There are laws from OSHA that regulate where you work - but no laws that regular where you sleep! It's all driven by money, of course...material with lower formaldehyde cost more to manufacture. Just walk into a Sherwin Williams and compare their paint. The highest ones are eco friendly "Low VOC" (volatile organic compound) - so industry definitely knows about it.

The numbers in my house were effectively off the charts and OSHA would be closing down your employer if you had this exposure at work.

Remediation for this is essentially allow to off gas, keep windows open. Off gassing also is impacted by humidity, so may be low during winter but high in the summer or when it rains.

Air filter DOES NOT fix this. The amount of air moved by a HVAC is peanuts compared to just opening windows for a few minutes.

California has regulations: https://ww2.arb.ca.gov/our-work/programs/composite-wood-prod...

You would be surprised how much particulate certain cooking methods produce, your home can go from 0 AQI to forest fire levels for a few hours without a filter.

With the right filter and sensor, you can keep your AQI in the single digits consistently and react appropriately to particle buildup. If you have a CO2 sensor as well you can react to CO2 buildup which is something I have experienced plenty of times in a modern apartment (not necessarily dangerous levels but levels high enough that cognitive effects should be expected). It is hard to keep indoor CO2 levels anywhere near outdoor levels without forced ventilation with the outside or living in a large house.

I have a xiaomi air purifier with AQ detector. Scrubber seems to to help with allergies. Detector itself is pretty much a glorified smoke detector Tamagotchi toy for me. I haven't found much use for it other than to keep numbers as low / nominal as I can. For which living in a pretty clean part of the city with good air quality means being more mindful when I cook to reduce smoke. That said the high AQ alarm has saved me a couple times from leaving stove top on / burning pots. Kind of paid for itself in that sense.

There was a time when my air quality sensor (a Temtop device) showed suspiciously high PM2.5 in the kitchen. It turned out the kitchen oven had too much oil build up inside and required cleaning. And no, I tried both cheap and expensive air purifiers; none of them could beat opening the kitchen window or turning on the range hood (a dedicated one, not the kind attached to a microwave). In this particular case, it was also a good reminder to clean the oven.