TOP indor polution sources from my 2 year experience with concentration detector:

- frying pan with just a bit of smoke, pm 2.5/10 goes hundres easy

- parafin candles, HCHO formaldehyde goes over 1mg/m3 (can't tell if other are better though)

- presurized cans (sunscreen, desodorant, shoe care etc) pm goes hundreds easy

- spray surface sanitizer alcohol based, registers high folmaldehyde too

And it's incredible how well air mixes in flat, spray in one room - few minutes later register in another. No fans needed.