[SML] Smoke vs Heat vs Rate of Rise detectors

[Dale Farmer]

On 3/8/2022 9:35 AM, Dougherty, Jim via Stagecraft wrote:
> I'll second the recommendation to include your AHJ, your alarm system contractor, and your Powers That Be early in the process.  Demonstrate the atmospheric effects that you use in your space - fog and haze will false trip many systems.  We underwent an upgrade some years ago and the decision was made to try a camera-based system; it was meant to be able to detect fire and flame by analyzing the video image (not a fire system engineer, don't know the details) specifically to avoid false activations through what we do.  It was pricey, we were early adopters, and it was a big investment.  Long story short, it didn't work.  It thought moving draperies/fog/a patron fanning themselves with a program were all flame and we experienced many false alarms, mid-show.  However, because communication was good throughout we ended up with a solution that works.  They were able to pull that system out and replace with other compliant equipment - primarily heat and rate-of-rise based.  The o!
>   nly trips we've had since were faulty sensors that were replaced and the troubles ceased.
> 
> Regarding the mist systems mentioned, I like the idea but why distilled water? Is there a large reservoir somewhere in the building to draw from? I'd think any benefit of it being distilled might go away over time in storage.
> 
> - Jim Dougherty
> Middlebury College Theatre Dept.
> 
> _____
   the reason for the distilled water, and yeah there is a storage tank 
that has to be periodically drained and refilled, is to make the system 
safe for use on energized electrical equipment.  Once the tank is 
drained, it switches over to regular water supply.   Regular water mist 
will have enough trace chemicals in it to cause short circuits in 
energized electrical gear. Especially if your area has hard water.

   The systems are sized such that it will extinguish expected fires, or 
contain them long enough for fire response to show up.  The huge benefit 
is that unlike halon systems, it is perfectly harmless to the meat 
machines that are also in the space, so you don't need to wait for the 
people to evacuate and the fire to get worse before release.

There is a video from a cruise line that was retrofitting these into all 
their ships.  They had engine room fires on a ship with a conventional 
halon system and one with the water mist system installed. Both very 
similar causes, a leaking diesel fuel spraying inside the engine.   The 
halon sysstem worked, and the fire was put put.  The ship needed 
emergency dry docking and was out of service for three months while the 
contents of that engine room got replaced.   Several millions in direct 
damage repairs, tens of millions of refunds of cruise tickets for that 
three month period.   The ship with the water mist system.  Fire was out 
before the firefighting team made entry.   Damage was confined to one 
cylinder of one of the two engines in that engine room, cleanup and 
repairs were completed at the next port call, mostly because they had to 
order the parts.  No lost time, repairs cost a few thousand bucks, 
cleanup was done with mops, buckets and rags by ships crew.

Here is the video.  They had a camera in the engine room that showed the 
fire breaking out and being extinguished by the HI_FOG system.
  https://www.youtube.com/watch?v=tKXiNdJMhgA

Also here is an article about a system installed in a historic property 
in the US.
https://www.securitysystemsnews.com/article/thomas-jefferson-s-home-gets-marioff-water-mist-system

Dale