Just getting around to reading this series. On the whole, it’s really well done. I wanted to make a couple of quick comments about low fog effects, though.

You mention Dry Ice, which certainly does what you talk about, but it’s not the only choice for this effect. Chilled Glycol fogs are also routinely used for this purpose. These fogs tend to hang around a little longer than dry ice, and as such can be a good choice for longer scenes.

The best technology for this effect, though is Liquid Nitrogen. Like Dry Ice, it uses a tank of hot water to create a very hot, humid environment. When the cryogen (whether dry ice or LN2) is dropped into the tank it creates a real cloud from condensed droplets of water. This cloud hangs around until it expands enough to reach its dew point, at which point it fully dissipates.

There are 4 major benefits to using LN2 instead of dry ice for this effect. First, CO2 is actually toxic at relatively low concentrations. Nitrogen is totally non bio-active, and you can use quite a bit more of it before it drives the O2 concentration to dangerously low levels. In practice, this will almost never happen, but monitoring systems can be put in place to handle it. Second, LN2 fog is totally dry, and doesn’t leave behind any wet residue on the stage like Dry Ice can. Your dancers will thank you. Third, there’s the amount of fog you can create. Liquid cryogens are capable of much larger effects than solid CO2. Most of the large scale spectaculars using low fog use LN2 for this reason. Fourth is a contractual issue. AGMA is allowing LN2 low fog on their stages, which isn’t true of other technologies. For this reason it’s now being used on both the LA & SF opera stages.

For more info, check out http://www.interesting-products.com. I work for the sister company (Designlab), and have a fair amount of experience with all of these technologies. Let me know if you have questions.