Fire alarm and detection VS. fog and haze

[BillConnerFASTC]

I wondered if anyone had come up with any better approaches. We recommend heat detectors only, no particle or smoke detectors, which should be possible in all but large return air ducts, where smoke detectors are required. We further recommend that those be zoned and and that it be possible for them to be silenced which generally requires notifying authorities and any central dispatching service, and may require a fire watch - either staff of the theatre trained and approved by the authorities OR a member of the fire service, usually an off duty fire person moonlighting.

Any other insights?

--
Bill Conner ASTC

 

[lwinters630]

No, but a great question. Fire watch its a P. I. T. . . .B.

 

[AEGProduction]

For some citys or districts, at least for schools, I have found that just asking the local Fire Department to turn the alarms off and monitor a school dance, sends someone over. There have been a few that have charged for it, but there are also a few smaller town ones that send someone over without a fee. I am sure this doesnt happen every weekend though, maybe once a month at that.

 

[MNicolai]

Not sure how code-worthy it is, but I know a local theater that manually overrides the particle detectors in their air ducts. The override resets automatically at midnight so when the fog/haze begins, the TD overrides the system. The if he should forget to remove the override before he leaves that night, it'll reset on its own.

To my knowledge, his fire department is not requiring that he have additional staff on fire watch nor that fire officials be present during those events.

 

[DuckJordan]

I wonder if they have another system in place. Fortunately in the venue I primarily work in the only detectors in the theater are heat detectors. though we do have particle sensors in the hallways (just means we keep the doors shut) To this day I've yet to see a show trigger the alarm system. The only time we are required to have a fire watch is when pyro is to go off during the show. Otherwise the fire system stays on and in place.

 

[BillConnerFASTC]

I wonder if they have another system in place. Fortunately in the venue I primarily work in the only detectors in the theater are heat detectors. though we do have particle sensors in the hallways (just means we keep the doors shut) To this day I've yet to see a show trigger the alarm system. The only time we are required to have a fire watch is when pyro is to go off during the show. Otherwise the fire system stays on and in place.

Are you sure you don't have smoke detectors in the return air ducts? They are required in all HVAC return air systems with more than 2000 cfm - which isn't much - considering a 500-1000 seat theatre usually has 20,000-30,000 cfm.

 

[MNicolai]

An article worth reading related to this topic:
http://www.systemsensor.com/pdf/case-studies/SSCS005-egyptian-theater.pdf

Another interesting couple pieces of information I learned from my brief research on this:

NFPA 90A 2012, 6.4.2.1

Smoke detectors listed for use in air distribution systems shall be located as follows:

(1) Downstream of the air filters and ahead of any branch connections in air supply systems having a capacity greater than 944 L/sec (2000 CFM)

(2) At each story prior to the connection to a common return and prior to any re circulation of fresh air inlet conection in air return systems having a capacity greater than 7080 L/sec (15,000 CFM) and serving more than one story.

NFPA 90A 2012, 6.4.2.2

Return system smoke detectors shall not be required where the entire space served by the air distribution system is protected by a system of area smoke detectors.

NFPA 90A 2012, 6.4.4.2.1

Smoke detectors used solely for closing dampers or for heating, ventilating, and air conditioning system shutdown shall not be required to activate the building evacuation alarm.

I cannot say with certainty, but some of the articles I found suggest that multi-criteria detectors are becoming excellent in at least their ability to distinguish dust from smoke. I would not be surprised if they were also capable of distinguishing water and/or oil-based atmospheric effects from smoke.

System Sensor in particular appears to be documenting this technology well:
http://www.systemsensor.com/multi/brochure/Multi_singlepage.pdf

Their multi-critieria detectors factor in:
1) Heat Detection, both temperature and RoR (Rate of Rise)
2) Infrared Detection, which specifically look at light levels indicative of flame signatures.
3) Photoelectric Detection, which examine the airborne particles.
4) Carbon Monoxide Detection, which looks as smoke toxicity.

The detectors then use algorithms to look at the reports being generated from each detection mechanism and determine if the various detection methods indicate a fire is present or not.

These advances in fire and smoke detection technologies may be making it much harder to achieve a nuisance alarm using theatrical atmospheric effects.

 

[Footer]

I get to play this game... a lot. Here is how ours is configured...

• We have detection on our grid and in our projection well, all are smoke detectors
• On each elevator door in each elevator lobby we have a detector, all smoke detectors except for the floor the stage is on, it has heats
• SL and SR we have an override timer. It is a 6 hour timer. When it is spun it disables the audible alarm in the theatre and keeps the firewall from dropping in case of a smoke head trip.
  • If a head does trip, it lights up on an anuciator panel USR. We then have to go inspect the are where the head tripped to varify that haze caused it, not a fire.
• We also have a pull station and an abort button SL and SR.
  • The abort will stop the wall from dropping if pressed within 30 seconds of the audible alarm
  • The pull station will set off the alarm and drop the firewall no matter what, override or not
• Whenever we are in override we are in a fire watch but no fire marshal has to be present.

There are particle sensors in the air ducts. We don't have an over ride on them. I have been told though that in years past they have been tripped...

 

[StradivariusBone]

I'm actually dealing with this right now. We have a group in today that's setting up truss with movers and wants to haze, but I'm concerned about it tripping the alarm, my administration is erring on the side of 'No'. I've never had it go, but I know it has in the building before and in other similar structures to ours. The fire watch idea is interesting and I'll have to consult with our fire inspector for our district to see if that's something we could do.

 

[marmer]

In Houston, when we want to do haze, we have to pay for and get a permit through the City, have an inspection by a fire marshal, and pay a City firefighter to watch the panel during the event. Then we can override the affected detectors. Our system is old enough that false alarms are kind of a concern.

This is enough to make me strongly discourage haze for most events.