"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."