All the HVAC smoke testers/creators are around 100bucks. The smoke in a can is about $10, but won't last long at all.

I'm wanting some source of smoke that I can spray around areas of my case, and see how it sucks in, moves through the case, etc...That way I can make fins/guides if need be.

Any idea's besides burnin things? I don't want to cause smoke stains/damage to my case and electronics...so I need clean smoke?