I've been on stages with smoke machines and I recall it being similar to how I experience vaping today.
NOTE: Several types of "fog" were studied including ones based on propylene glycol (aka "vape").
As singer and/or athlete's they felt entitled to working in a "clean" environment.
"In 1994, the National Institute for Occupational Safety and Health published a study of 224 actors in Broadway productions that ruled out theatrical fog as a cause of asthma. Dryness and throat irritation in "some individuals" was the limit of the problem, the study concluded. "
The results of the 1994 CDC study are here:
A variety of "glycol" vapor was studied including those that today are considered unsafe, such as ethylene glycol.
"Based on the results of this study, there is no evidence that theatrical "smoke," at the
levels found in the theaters studied, is a cause of occupational asthma among performers.
Some of the constituents of theatrical "smoke," such as the aerolized glycols and mineral
oil, could have irritative or mucous membrane drying properties in some individuals.
Therefore, it is reasonable to minimize exposures by such means as relocating "smoke"
machines to avoid exposing actors to the direct, concentrated release of the aerosols,
minimizing the amount of "smoke" necessary for the production, and using only fog
fluids approved by the manufacturers of the machines. The glycols used should be at the
level of "food grade" or "high grade." Glycol-based systems should also be designed to
heat the fog fluids only to the lowest temperature needed that achieve proper
aerolsolization. This would help to avoid overheating the fluid and minimize the
generation of decomposition products."
Note the underlined portions.
Standard, modern VAPE tech from OSHA.
How interesting is that?
Poor S.O.B.'s doing the current formaldehyde testing are violating OSHA's idea that the temperature needs to stay "low."
Note the use of "food grade" or "high grade" glycol, e.g., USP.
Now this is not a "big win" for vaping but it shows that breathing glycol fog has been around for more than twenty years and is quite safe. Particularly since these technologies are still in use today.