Re: How dangerous is theatrical smoke?

It depends. Theatrical smoke can be made from water vapor, which is safe. It can also be made with liquid nitrogen or carbon dioxide (from dry ice). In both these cases, the fog is made when water vapor in air condenses. Because air is 80% nitrogen, as long as the nitrogen from nitrogen smoke machines is not concentrated (so that there is enough oxygen in it), the smoke is safe. Likewise, the smoke from using dry ice is made mostly of condensed water vapor, so it is safe, as long as there are not high concentrations of carbon dioxide, which at high concentrations can be deadly. So as long as the smoke is mixed with air, there should be no toxicity.

There are other compounds used to make theatric smoke include glycol, glycol/water mixtures and pyrotechnic smoke (from fire). These can be irritating the mucus membranes in the mouth, nose and lungs. In addition, they can cause long-term damage if someone is exposed to them regularly, like stuntmen and people in Broadway theaters if they in a long-running play. However, when one is not exposed regularly to the smoke, chances are that the fog won't cause anything more than temporary irruption to nose, mouth and throat.

Wikipedia has a good article at http://en.wikipedia.org/wiki/Theatrical_smoke_and_fog.

Thanks for an interesting question.