As
@Rob562 said, it depends on scenario, scale, and location. I wish to add to
his list that compressed CO
² has been used as well as a method of using a combination of clear or tinted transparent material with upward facing fans and proper lighting to accomplish these effects. There are others...
Choosing the right fog, or smoke effect method is very important for any installation, so here are a few of the things to keep in mind when selecting and designing indoor fog, haze, or smoke effects:
- When using glycol based fog, know that it could leave slippery residue that could cause slip & falls.
- When using any fog system, make sure there is appropriate ventilation for the show area and keep the fog density to a minimum, especially in areas where guests have to breathe. CO² and Glycol-based fogs can suffocate a person in rapid order unless you manage airflow adequately.
- If using water mist, pay attention to the floor and surroundings to avoid mold, mildew, rot, and even guest slip & falls.
- Pay specific attention to electrics and lamps to insure the fog doesn’t cause lamps to blow prematurely, or cause electrical shock hazards to maintenance personnel or guests.
- Never use pyrotechnic methods indoors, unless you are licensed and have obtained all permits for intended venue.
An interesting lesson learned in the mid 80s in EPCOT was in regards to the Transportation Pavilion.
There was a cool scene at the end that had a large diorama of a futuristic city with flying cars and huge skyscrapers emerging from a low-lying fog. The guests where moved around it in a half-circle so they could get a really good view of this city of the future. With the lighting and fog it was quite awesome.
During the construction of EPCOT- which continued long after its opening - everything was so behind schedule, that in some places they just threw stuff together by the seat of their pants. This particular scene was thrown together that way. It’s what we call an “as built” design, meaning it was designed on location as it was constructed.
Being in such a hurry, the entire raised floor of this room was built as a wood riser, topped with 3/4” plywood upon which this giant model was then built. A couple of years later, it became apparent that the water mist used to create the continuous fog had caused the plywood base to rot and warp, causing show maintenance to shut off the fog boxes and shore up the base of the diorama to keep it from caving-in on itself.
- Chuck