# Fog/mist effect without setting off fire alarms



## FogMan (Apr 18, 2013)

Hello hello,

I'm new to the forum!

I am trying to recreate a foggy New York riverside scene onstage and would like to utilise a fog/mist effect, so that thin clouds roll along the floor. However, machines that create such effects have been disallowed by the theatre, as they fear they will set off the fire alarms.

I am looking for a way to achieve such an effect without setting them off. Does anybody have any ideas? My current thinking is to perhaps experiment with lights. An animation wheel was suggested to me; does anybody understand what this is?

Thanks everyone!


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## TheaterEd (Apr 18, 2013)

a couple pounds of dry ice and a fan?


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## Markovich (Apr 18, 2013)

uhhh how does fog set off a fire alarm in the first place, from what I know its actual fire that sets off a fire alarm. not fog.


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## Les (Apr 18, 2013)

Markovich said:


> uhhh how does fog set off a fire alarm in the first place, from what I know its actual fire that sets off a fire alarm. not fog.



Depends on the detector. Some detect particulate, which is what fog is.


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## Markovich (Apr 18, 2013)

I learn something new everyday. LOL.

maybe low laying fog might be the answer.


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## ruinexplorer (Apr 18, 2013)

It may be the answer if you are using a dry ice fog and not a chilled fog fluid. The reason I say this is that if you have an orchestra pit, you may have an air return with a possibility of sensors within the ventilation system. I found that out the hard way when we were doing a production of A Christmas Carol and had a very foggy graveyard scene. All the chilled fog was dumping into the orchestra pit so as not to go into the audience, but was being sucked up by the air return and set off the alarm.


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## Amiers (Apr 19, 2013)

I also had a run in a the last place I worked. We had POTO running the graveyard scene and the AC intakes are on either side of the stage in the wings and it sucked up chilled fog. There were fire alarm sensors in them and well lets just say the fire dept wasn't happy. We still ran the fog but turned the AC off for that run of the show and all was good. You might check with building maintenance and ask if they have those sensor and if possible turn off the AC and do a test run(also alert the fire dept naturally)


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## MPowers (Apr 19, 2013)

Markovich said:


> uhhh how does fog set off a fire alarm in the first place, from what I know its actual fire that sets off a fire alarm. not fog.



There are a number of ways a device can trigger an alarm. Some detect particulate matter in the air, "smoke Detectors". Some detect chemical concentrations in the air such as metal oxide CO2 detectors, some detect electrical conductivity in the air. Others detect a change in opacity or color due to chemical changes caused by the item being detected. There are direct temperature devices such as fusible links and there are "Rate-of-Rise" dectors which measure how fast it is getting hotter. Most "smoke" detectors are designed to trip an alarm while the fire is still in the smouldering phase, before there is actually a "fire". 

The reason fog and haze are such a problem is that many modern buildings have particulate detectors installed within the HVAC duct system in a return vent where smoke from a real fire would tend to collect in the early stages of the event. Auditoriums built without knowledge of entertainment industry devices and techniques have these units installed above the stage where rising apmospheric effects are most likely to be concentrated. If they are designed without a bypass or method of temporary and/or remote shut-off, they will trigger every time you hav a light show with haze or similar.


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## cprted (Apr 19, 2013)

Markovich said:


> uhhh how does fog set off a fire alarm in the first place, from what I know its actual fire that sets off a fire alarm. not fog.



Not all detectors are created equal. Some are heat detectors which set off the fire alarm if they detect changes in temperature. Others detect particles in the air (ie, smoke, dust, etc) and there are a new breed which use infrared to detect smouldering fires. Knowing what type or detectors are in your facility and how the work is important when you start using fog, haze, pyro etc, indoors.


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## Robert (Apr 21, 2013)

I use a fast dissapating fluid for all of my smoke effects in my spaces. Only had one issue when someone blocked the outlet on the fogger in a rehearsal and it sent all of the smoke offstage into the green room area. Physical plant and campus police had been notified in writng prior to the rehearsal. I called them an alerted them to what happened and they responded knowing that it was potentially a false alarm. I always test these effects with notification to the alarm company, in house mechanical staff, and police department no matter how little fluid I plan to use. Just to CMA. One space has smoke detectors overhead in the loft, the auditorium, and tech booth. The other only has a detector in the air return.


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## SteveMcQueen (Apr 21, 2013)

Couldn't you just turn off the alarms? We use a ton of fog for each show, and turn them off. The. We have an usher wall around during the show, making sure there is not a real fire.


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## venuetech (Apr 21, 2013)

FogMan said:


> I am looking for a way to achieve such an effect without setting them off. Does anybody have any ideas? My current thinking is to perhaps experiment with lights.* An animation wheel was suggested to me; does anybody understand what this is?*



the suggestion likely refers to any number of lighting fixture accessory that create some sort of moving effect (fire, clouds, rain, water reflection) this could be a gobo rotator, or something like a GAM Film/FX but I don't see how any of these could be applied to your situation.


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## Esoteric (Apr 21, 2013)

SteveMcQueen said:


> Couldn't you just turn off the alarms? We use a ton of fog for each show, and turn them off. The. We have an usher wall around during the show, making sure there is not a real fire.



Depends on the locale.

At the church that I personally attend the municipal code requires you to hire the Fire Marshal or an approved substitute if you are going to turn off your fire alarms.


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## Les (Apr 21, 2013)

SteveMcQueen said:


> Couldn't you just turn off the alarms? We use a ton of fog for each show, and turn them off. The. We have an usher wall around during the show, making sure there is not a real fire.



Do they check inside the walls and attic too?


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## Betty Dilley (May 5, 2016)

Thanks. We will try that.


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## RonHebbard (May 5, 2016)

TheaterEd said:


> a couple pounds of dry ice and a fan?


Dry ice sublimates directly from a solid to a gas but I suspect Ed's implying you use it to chill mist from a fogger keeping the mist cool enough that it won't rise high enough from the floor to annoy your smoke detectors. If you do annoy the smoke detectors it's amazing how quickly the fire folk appear and how little sense of humor they possess. You'll have better results if you chip your dry ice to maximize its surface area for better, faster, chilling. Some dry ice sources offer blocks, sliced blocks and chipped/crushed dry ice.
A cautionary note: Many users bring in fresh ice daily on performance days. If you bring in a larger quantity to get through matinee days and/or weekends when the supplier is often closed, DO NOT store your ice in a sealed, air-tight, container! When the ice sublimates from a solid to a gas, its gaseous state occupies more volume. In short: An air-tight dry ice container equates to a bomb. Decades ago I witnessed the result of someone building a nice, insulted, sealed container to store their dry ice in. Friday afternoon he picked up enough dry ice for Friday evening plus three Saturday performances and two Sunday performances. By Saturday morning the securely sealed lid had blown off the container and there was only enough ice remaining for Saturday's performances. Of course the welding supply store wasn't open on Sunday but the local Red Cross blood and organ transport center was.
Toodleoo!
Ron Hebbard.


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## RonHebbard (May 5, 2016)

Markovich said:


> uhhh how does fog set off a fire alarm in the first place, from what I know its actual fire that sets off a fire alarm. not fog.


Heat detectors and rate of rise detectors don't care much but some, cheaper, smoke detectors are less selective. To many smoke detectors, smoke is smoke and so is fog. I have embarrassing first hand experience with flat black spray cans, smoke detectors, sirens and irate fire fighters. Try it yourself if you like but I wouldn't recommend it.
Toodleoo!
Ron Hebbard


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## Malabaristo (Aug 22, 2019)

This seems like as good a thread as any to add this question: does anyone have any experience or data on smoke detectors being affected by fog or haze over long term use (even when disabled)?

The claim was made that sensors would need to be physically covered or removed and reinstalled rather than just being put into test/silent mode because the fog residue would build up in the sensor and eventually cause nuisance triggers down the road. Ionizing particulate sensors were specifically mentioned as being susceptible to this, while photoelectric sensors were supposedly safe to leave exposed.

Now, intuitively this seems crazy for normal, theatrical use of these effects. Maybe if you're a club that likes to make the dance floor opaque with fog all night every night, then there could eventually be a problem. If you're going to that extreme, though, then I don't see why photoelectric sensors would be any better....

So, what evidence could I provide to refute this? Unfortunately, this isn't the sort of person that is willing to listen to anecdotal experience and common sense.

Obviously fire watch procedures and other safety rules apply the same either way, but some of the sensors are very difficult to access and the labor costs would just make this prohibitive.


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## What Rigger? (Aug 24, 2019)

SteveMcQueen said:


> Couldn't you just turn off the alarms? We use a ton of fog for each show, and turn them off. The. We have an usher wall around during the show, making sure there is not a real fire.


Your local building codes, laws, AHJ, etc... may not require more than this. Others may differ. This sort of thing should be treated on a case by case basis with whomever the local fire authority is.


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## macsound (Aug 26, 2019)

I'm not suggesting this as a solution but rather a story based on a theatre that didn't know how to survive building rentals if they completely outlawed fog and haze.
All smoke detectors located over the stage were covered with a paper dixie cup and gaff tape.

In designing and building new theatrical / entertainment / worship spaces, I firmly believe there should be a legal solution to atmospheric haze. 
Currently our solution is 1. hoping for the best or 2. use no haze or 3. partially disable fire system.
Some solutions could be time based deactivating certain zones of detectors and realizing haze is a real thing and don't put particle sensing detectors in these spaces.


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## Malabaristo (Aug 26, 2019)

The weird thing about this situation is that we can all agree on how to handle the partially disabled system (fire watch & some improvements to how we assign/train people for crowd management). The point of conflict is the idea that exposure to fog/haze effects is going to somehow shorten the life of the smoke detectors if we don't physically remove them from the room. The cost of hiring an electrician to do that before and after each performance adds up to an impractical expense for most shows, and seems obviously unnecessary to me. I'm hoping to find something I can point to as evidence that it's not just my opinion.


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## RonHebbard (Aug 26, 2019)

macsound said:


> I'm not suggesting this as a solution but rather a story based on a theatre that didn't know how to survive building rentals if they completely outlawed fog and haze.
> All smoke detectors located over the stage were covered with a paper dixie cup and gaff tape.
> 
> In designing and building new theatrical / entertainment / worship spaces, I firmly believe there should be a legal solution to atmospheric haze.
> ...


 *@macsound* You're taking me back to high school in the 1950's when our Board of Ed' retrofitted our 1912-ish high school with rate of rise detectors throughout without taking into account how quickly neither a 2 Kw incandescent follow spot can raise the temperature 3' directly above its tail end in a five by five booth nor two electric tea kettles and a two burner hot plate in the staff room. 
In a matter of weeks, those two detectors in particular were exchanged for alternate detectors. 'nough said. 
Toodleoo! 
Ron Hebbard


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