fog on stage


Well-Known Member
I would really appreciate your help on this one, we are doing the show Anton in Show Business. In the opening we were planning to use a fog machine with a fog chiller, but during rehersal today, we set off the fire alarm, they installed a new system over the summer, and almost anything will set if off, we've tried dry ice, but the building is so dry it dissapears almost instantly, any suggestions would be greatly appreciated. we open wednesday.
Whenever I have to take smoke into a venue (I run a mobile DJ & Lighting service), I always ask if the smoke detectors in the immediate area can be disabled for the duration of the show. If not, I then see if the alarm can be operated in silent mode.

In most cases, this call can be made by the building supervisor or duty manager. In the US however, you may need to seek the advice of a fire marshal or similar.

I hope this is helpful
Im not sure if this would work but try using a lower density fog fluid. I know there are products out there that are called "molecular fog fluid" or somthing along those lines.
Theater Ninja
Going along with Mayhem, you can ask to have have to fire alarms put on test or silent. Depending on how your school runs they usually have to pay a fire fighter to be on call during the run of the show or have someone be in the fire pit so when an alarm goes off they can check the area then if it is a true fire, then they will have to call it in.

By turning the fire alarms onto test, what it does is when an alarm goes off, the fire department ignores the alarm unless someone calles it in. To do this, usually you have to call the fire department and tell them a code that is set up with them.
The fire alarm is a pretty important thing to keep in mind, my school forgot all about it and was testing the fog maching and the firefighters were there withing 5 minutes. Another thing, most are looking for a cheap way to do low lying fog and not the expensive way, but our school did the expensive way. We have someone at out school that does the professional lightings for the president and many concerts across america and we used their hazer. It was ok but did not stay low, it filled the entire area and adventually left the theatre through the ventalation shaft. Haze doesn't set off fire alarms but fog does, so be aware before doing it.
If you can cool the fog by routing it through a chest of ice, then the fog won't rise.
I think some fire alarms are more sensitive than my youth group. once i was cleaning a fog machine (they tell us to run some vinegar through them to kinda clean it out, you endup with some diluted fog fluid in the thing, not all vinegar and not all fog fluid, so it doesn't gunk up or anything.) (supposedly) in a back room and the door shut, unbeknownst to me. (usually the machines are cleaned outside) the room filled with, i was so scared the alarm would go off! i grabbed a box fan, opened the door, and stood there tryng to blow the fog out for maybe 10 minutes, i was so scared...but, it didn't go off......go figure.
The best way is a Low Smoke Generator, which you may be able to rent. But bring your checkbook. Also, you'll need a tank of liquid nitrogen or CO2, which you can get from a welding supply house.

As for shutting off alarms, etc. better check with your facilities manager before you start with that stuff.
Haze doesn't set off fire alarms but fog does, so be aware before doing it.

Not true. Haze is basically a thinner version of fog or smoke. Haze, depending on the sensitivity and type of your fire alarms, will set it off. Most the time to set off a fire alarm with haze you have to have a large buildup.

Also, if you use laser fire alarms in your theatre ceilings, watch out they dont like haze at all. However, you can have an electritian come in and turn down the sensativity of the lasers, as long as its within fire code.

Smoke alarms can do odd things. We did a show late last year. The second scene involved a small (and not very dense) volume of smoke rising through the floor. In testing, we filled the theatre with smoke - no problem. The next day we ran it for 3 seconds to show the director and set the alarm off. All that week the cast had been buring half a newspaper on-stage for the final scene with no problem.

Moral of the story: Smoke alarms do funny things. The only way to make sure and not disrupt the show is to have alarms turned off for all rehersals and runs.

However, this is easy enough for us to do because all our alarms are local only, and security canturn them off. If they do go off, security don't get into a panic if they know we're in there.

Alarms connected to the fire department: My advice is get a key to be able to turn them off as required, rather than take the risk.

Apparently, audiences don't like the fire trucks pulling up outside theatres.
The Antari Ice Fogger seems to work well for me and allows you to change output density. It chills it well and disperses well, but be sure to use their special fog juice for low line fog.

Also, many places allow the temporary covering of smoke detectors. They normally cover ours and if there is a fire and the smoke gets bad, it'll find it's way in.
Dale said:
Does it not depend on the size of the smoke particles to set off the alarm?

Not really. There are two types of smoke detectors (quoted from
Ionization Detectors
Ionization Detectors works by forming an electrical path inside the smoke detector with a very small amount of radioactive material. When smoke enters the detector, the smoke molecules attach themselves to the ions and change the electrical current. This change in the current triggers the alarm.

Photoelectric Detector
Photoelectric Detectors work by containing a light source (like a small light bulb) and a photocell that is activated by light. Usually, the light never reaches the photocell. However, when smoke fills the smoke detector, the smoke reflects the light towards the photocell. The photocell than triggers the alarm.

Which is Better?
Both of these types of smoke detectors are designed to detect smoke in the air. The ionization detector responds slightly quicker to flaming fires (like draperies), with smaller particles of combustion, while the photo-electric detector responds quicker to smoldering fires (like a cigarette.) However, both types of smoke detectors have to pass the same test to be certified as a UL smoke detector, and both will warn you in almost all cases of fires.
In essence, it's not a matter of the size of the smoke particle as much as how fast they detect the smaller smoke particles vs the percentage of smoke in the air.

In our theatre, they wisely installed heat detectors over the stage area, which is wonderful... but the house uses smoke detectors - so anything that goes into the house can set them off. Haze isn't likey to set it off, but over time (like the entire course of a show) it could. Our theatre had a smoking section back in the day, and the alarms didn't go off with that. The HVAC (air conditioning) system keeps the air moving enough that a light haze or cigarette smoke won't set it off. But, as the detectors age, they got more sensitive (as long as they're kept clean).
At my school, my drama director is fogaphobic. She hates fog for some reason. Even if we are able to get the fire dept. to durn off the alarms, she is still scared. So, we just have to live without fog.

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