A few weeks ago, a technician from a regional opera company called the ESTA office with a list of questions about liquid nitrogen fog technology. Did the nitrogen vented from the storage dewar tend to pool, as butane will when released from an LP gas canister? (No, and it won't burn, either.) Would it be okay to store the liquid nitrogen dewars in an understage trap room? (Yes, if there is good ventilation.) Is the gas toxic? (No.) His questions went on and on, and he listened to the answers. It was good that the technician made the call with his specific questions about liquid nitrogen, but he might have had a better grasp of his fog-making choices if had a better background knowledge of the different cryogenics used in making low-lying fog effects—their advantages and disadvantages, benefits and hazards—and also about what standards and regulations he might need to discuss with a local safety inspector.
“Handling Cryogens Safely” is an ESTA session scheduled for Friday, October 24, from 11:00am. to 12:30pm at LDI that is designed to give people basic information about using dry ice, liquid carbon dioxide, and liquid nitrogen—the three major cryogenic technologies used in fog production—safely, and information for meeting regulatory requirements and concerns of local inspectors when those arise. The session will include presentations by Martin Michaud of MDG Fog Generators, Don Phillips of Le Maitre Special Effects, and Larry Schoeneman of Interesting Products, talking about liquid carbon dioxide, dry ice, and liquid nitrogen, respectively. Yours truly, Karl Ruling, will serve as the moderator and will explain briefly how the cryogens are used to make theatrical fog. The panelists are from Canada and the United States, and have links through business partners all over the world, so the panel will be able to offer somewhat of an international perspective, but will focus on North America when dealing with regulations.