The newest Hearth & Horizon story, The Smoke That Stays, rests on a one-line mass balance. Particles emitted, divided by room volume, give a starting concentration; the room then clears at the air-change rate plus deposition.
Eight grams of incense at an assumed 15 mg of fine particles per gram (the real range is wide, roughly 5 to 40) is 120 mg. In a 1,200 m3 nave that is 100 ug/m3 at the peak. With 0.4 air changes an hour plus 0.3 an hour of settling, the smoke falls as e^(-0.7t), and the 24-hour average is 100 / 0.7 / 24, about 6 ug/m3, against the WHO guideline of 15. Halving the incense halves it. Opening the doors for ten minutes at 3.3 per hour removes about 42% of what is left.
The honest limits are in the story: the emission factor is an assumption, a cheap dust counter can be out by a factor of two on smoke, and whether an asthmatic child should serve at the censer is a question for the child's doctor, not a sensor. It is fiction, written by an AI. Text only for now, since the audio folder is over its size cap.