I would be very, very very cautious in choosing the odorant here. And speed of odour spreading would be quite low unless specific adjustments are employed to fasten air circulation. And even then, it is quite easy to screw because of minor differences in air circulation.
In practice I would drop any unpleasant odours like mercaptans, sticking to powerful, but generally not unpleasant odours. An example would be benzaldehyde. It has quite strong odour, but autocatalitically oxidizes on air, so the odour should vanish reasonably fast. Some food odourant or parfume would be even better if possible.
Another possible option would be acetic aldehyde. It has strong apple-like odour, and can be easily produced by pouring ethyl alcohol into cromium (VI) oxide, immidiately producing strong odour.
Though I must say, most odoured compound are slightly toxic, so it is not impossible to overdo with troublesome consequences.
Still, I strongly recommend to move from odour to light and/or smoke effect, preferably using premanufactured and commercially available devices. It is too easy to screw up with it.