I’m melting… inhaling carbon dioxide

Dear Elphaba,

Congratulations on your awesome role in the production! And congratulations on checking to see if getting sprayed with carbon dioxide (CO2) nightly for several weeks would be harmful to your health. While the Wicked Witch melting in a cloud of swirling smoke is a wonderfully dramatic scene, it is good to know the facts about CO2.

CO2 is naturally present in the air at a concentration of about 0.035 percent. Short-term exposure to CO2 at levels below two percent has not been reported to cause harmful effects, but higher concentrations, like you might be exposed to when sprayed by a fire extinguisher, can affect respiratory functioning. In addition, high concentrations of CO2 can cause the central nervous system to be simultaneously stimulated and depressed, a phenomena that can have dangerous results.

Your body responds pretty recognizably when it has had more than its desired dose of CO2. Breathing CO2 concentrations of four to seven percent has been shown to produce headaches, hearing and visual disturbances, increased blood pressure, difficulty breathing, mental depression, and muscle tremors. As CO2 concentration increases, its effects become more dangerous and symptoms occur more quickly — exposure to seven to fifteen per cent carbon dioxide can produce drowsiness, dizziness, and unconsciousness within a few minutes. At 17 to 30 percent CO2, people  have experienced loss of controlled activity, unconsciousness, coma, convulsions, and death within a minute. Several deaths have been attributed to exposure to concentrations greater than twenty percent. As you can see, playing around with CO2 could be a risky endeavor, with very little margin for error.

If you start to feel shortness of breath, choking sensations, dizziness, or any of the other associated symptoms, you should remove yourself from CO2 exposure right away and get some fresh air. If you're in a well-ventilated room, or can have a fan near the stage to blow away the "smoke" your exposure may be lessened, but because CO2 fire extinguishers have a high concentration of carbon dioxide, it's probably not be the best option.

Have you talked to the visual effects coordinator to discuss this and other potential options for the scene? Or chatted with the director regarding your concerns? For a safer choice, you might consider using a fog machine, which creates smoke out of water vapor, or a commercial smoke bomb, which does not use CO2. Poking around on the internet for theater tricks for safe ways to create smoke or fog could turn up some interesting results. But for now, it might be best to stay away from the CO2, so you can play many roles after this one.

Break a leg (but not a lung),