Let me talk a bit about atmosphere effects... Now, I'm not going to get in to the health issues associated with these effects in this post, but be aware there are some systems that have been proven to be problems in that department, so if you are going to use one, find out what the story is on it first...
What I want to discuss is the hassle associated with these effects... (I'll get to today's little nightmare in a bit...) There are a few different types... 'Haze' is sort of like an all over effect, that just makes things a little blurry, and highlights lighting beams really nicely... 'Smoke' tends to be fairly dense when created, it will eventually dissipate in to a haze, or it may simply get blown away (by any number of means) before it breaks up. It is pretty opaque... 'Fog' is similar to the smoke, but is usually chilled so it hugs the floor. Depending on how it is made, it may simply evaporate into nothing, or it may warm, and turn to a haze before going away...
Here's the thing that they all have in common... They all are based on some type of particle that is suspended in the air... Some do that with water vapor, some with oils, or glycerines... The particle reflects, or refracts the light, so it will be visible... Now, here's what makes these things absolutely miserable in my book... Smoke alarms are designed to detect smoke, which is combustion products, mostly very fine ash... Smoke alarms can not tell the difference between real smoke, and an atmospheric effect... Smoke alarms are everywhere folks, which is good, until you are trying to make your theatre smoky/foggy/hazy... Then they are a royal pain in the ass...
Tonight, I was running an event that had a hazer specified as part of the show. Today, I asked the administration contact I have about the fire detection equipment in the space... I was informed that the sensors in the space are heat detectors, rather than smoke detectors... That is pretty common in a number of theatres now as the atmospheric effects have become more prevalent... Tonight in the middle of rehearsal (thankfully no audience) the alarms went off... No less than 5 engines, and ladders showed up, along with a chief, and an assistant chief... I'm thinking it must have been a slow night at the fire house, but whatever the reasoning, they all came... They were thankfully very cool about the situation... They did inform me that contrary to what every singe rat bastard that I asked told me, not only are all the sensors in the space particle based detectors, but that it is policy in those spaces that no smoke/fog/haze machines are to be used... The client was less than happy when I informed them that there was no chance in hell I was going to fire up the hazer again until I had something signed by the administration, and the fire inspector detailing that there was some kind of waver of the policy... The lieutenant informed me that it is possible to hire one of the firemen during the show, which would allow us to deactivate the smoke system in the theatre... That is my preferred option if I can't simply get them to cut the effect... Why?... Well while setting off a fire alarm that rousts at least one fire house is embarrassing at the least and dangerous because they may have to respond elsewhere at the worst, there is the unforeseen aspect of an alarm going off in a full theatre... People have this annoying tendency to panic in that situation... Even if there isn't a fire, that panic can result in a lot of people getting injured, or worse...
For my nickel, most people don't need the effect... Those that do need the effects have a tendency to run them too long... Its theatre folks, its about the willing suspension of disbelief... If you give people the slightest hint of the smoke or haze, their minds will do the rest if your show is done well... If you are trying to hide your crappy show behind "big" effects, you need more help than some suspended particles...