Smoke machines have been used to create atmosphere since Shakespeare's Globe Theatre in the early 17th century, where a clever combination trap doors, fans and chemicals were used to suggest the presence of magic. That process has been greatly simplified over the years, and what would have taken a team of stagehands a considerable amount of effort to pull off is now available in a range of compact, and immediate devices.
Modern smoke machines use a non-toxic chemical and water solution which is pumped into a heat exchanger, where it is vaporised. The result is a cloud of dense vapour that hangs atmospherically in the air. Advanced units may also include variable speed pumps, timers, or remote operation modules.