Cheap little electric fog machines are on sale everywhere this month for Halloween decorating, they run on a glycol based fluid which should not trip most smoke detectors, that's also cheap to buy now, usually on the same shelf. We're talking like thirty dollars, maybe less, at Walgreens, Walmart, Target, etc. Could be worthwhile to pick one up on sale and store it for that occasion down the road where you need to make some shafts of light pop out in a scene or add some live smoke to a digital fire scene, or frost for a "cold" scene composite, to help sell the illusion. Cheap in October. But just try to find one of these for a reasonable cost in mid winter or spring.... hard to do. Buy one this month, even if you won't need it right away, it's a value.