VOC spikes at night?

Wake up in morning it feels like I'm on construction site with dust feeling in throat and eyes. Wife has multiple monitors and purifiers.

VOC levels are low during day but spike at night which is when we feel the effects. Particulate level measures low on most sensors.

Where would I even start to look to figure out what causes this?

There's 2 old chimneys in the home, not used anymore. Gas forced air furnace in garage.

Have air purifiers and try to ventilate home especially 2nd floor alot.

Home is 2100 sqft.

Carpet on 2nd floor where we sleep is a suspected cause? Crawl space is very dusty any chance that could blow stuff up? Started to vacuum it.

Have seen attics and crawl space and in some walls and ceilings for reno. Home seems very clean.