How often does the smoke alarm in the bank call the police?
See the alarm threshold, in which case the alarm will be given, and whether the particles in the air will reach the particle size detected by the detector.
It's OK for several people to smoke at the same time. When they don't reach a certain concentration, they won't call the police
The mosquito will not have a problem unless you directly to the mosquito coils on the smoke will be lower, quite a lot of smoke will be below that point, unless many than not, 20 square meters will not have problem, unless the smoke problem!
