[bennyg]

Is that short burst of deodorant actually harmful or do the numbers just go up a lot?

[theshrike79]

It measures the amount of particles in the air, it doesn't analyse their content.

Just having an ultrasonic humidifier in the bedroom makes the PM25 counter jump from 1-2 to 200-250.

[amluto]

An ultrasonic humidifier turns whatever impure water you feed in into tiny aerosols, from which most of the water quickly evaporates, leaving even smaller aerosols behind. Those likely consist of soluble salts (likely not terribly harmful) and bacteria (possibly quite harmful).

I would avoid using them unless, perhaps, I ran the output through a filter. Or I would use an evaporative humidifier instead.

[wasmitnetzen]

Alcohols are VOC's and many deodorants contain them. They are probably among the less harmful VOC's.