January 20, 2008
Museum fire prevention: gas vs sprinklers
I wonder if this makes sense:
A new sprinkler system is being installed at Watkins Community Museum of History.I'd think that if properly installed, a gas system would be no more vulnerable to accidental discharge than sprinklers. It is true that museums can do much to minimize the risk of water damage from sprinklers by insuring vulnerable object are not left uncovered in the open, but it still seems that gas systems offer a huge advantage not just in the ease of cleanup but also in the greater sophistication of their triggering mechanisms. Sprinklers are normally temperature-actuated, requiring some serious heat before they go to work.The $75,000 system replaces a 10-year-old FM-200 gas system used to put out fires in the 120-year-old building at 1047 Mass. The switch from gas to water is being made after a lightning strike two years ago caused most of the gas to be expended when the suppression system was set off. There was no fire and no damage from the lightning strike.
The hydrofluorocarbon gas in five of six tanks at the museum was expended at the time of the lightning strike. They were not refilled because of the expense, leaving only one tank for fire suppression. It would have taken about $40,000 to refill the tanks, Rebecca Phipps, museum director, said.
"We decided it would be better to go with water," she said.
The sprinklers are being installed on the top three floors, which includes the storage area for artifacts that are not on display. Once installed, the system will not protect the lower two floors or the basement.
Posted by David on January 20, 2008 10:36 PM
In "pre-action" water systems, you have the usual thermal break bulbs at each sprinkler head, plus you have (if you design it that way) either smoke detectors or products of combustion detectors which control a pre-action valve...so the pipes stay dry until and unless the system has pretty good reason to believe theres an actual fire, and only the sprinkler heads directly over the fire open when they sense the heat. To be extra sure you can design the system so you must have any combination of smoke and products of combustion and heat rise of a certain rate before the system pre-activates, and you can put those detectors where you choose. It's not just "apres-mois le deluge" anymore.
Posted by: doug in colorado on January 21, 2008 10:50 AM
you made the correct action if you want to protect the building but if you want to protect the exhibits , youre wrong because the water may cause more damage than a smal fire controled early by a gas system.
the spinkler systems and the gas systems are not made for the same vocation.
Posted by: audet on January 21, 2008 11:35 AM
Gas systems are most effective where the space can be enclosed to retain the concentration of gas (or maintain the exclusion of oxygen).
It takes a lot of gas to protect an entire floor of a large museum or even a good sized room, and because of the hazard to humans, you normally have a time delay to allow evacuation before gas release, and/or a combination of heat rise, smoke, and combustion (ionization) detectors as I described, so you don't fatally gas a group of patrons when some teenager is playing games with one smoke detector or someone drops a lit ciggy in the wastecan. Water systems make more sense in those cases...The alarm sounds first, then the pipes fill with water, retained by the sprinkler heads...if it's small enough to fight with a hand held extinguisher, you do that...if it's bigger, the fire triggers the one or two heads directly over the fire. If you're protecting the Mona Lisa, a small room with a gas system and an automatic door would make sense...in a larger gallery with less precious art/artefacts, pre-action water makes sense.
Posted by: doug in colorado on January 22, 2008 11:39 AM
First of all a nice mature thread of information and logic from you all. The debate fire vs gas is a comment that I receive from Clients. In our project we have implemented water with a double knock. We have smoke sensors in the floors and ceiling --> Smoke Alarm is triggered --> second knock fill the pipes with water --> now wait for sprinkler bulb to break and only spray water in the localised area. I agree that after first alarm, determine whether you can kill the fire with a fire extinguisher. The feedback we have had about gas, need a perfectly sealed room oxygen content must go down below 12%, expensive, has corrosive qualities on computer equipment?.
Posted by: Peter Mills on February 6, 2008 11:15 AM
Some of the gas systems can generate a corrosive product in the course of extinguishing the fire...the agent is partly consumed and the products of combustion can be corrosive
...some don't...depends on the system/chemistry.
Posted by: doug in colorado on February 18, 2008 11:37 AM
cronaca.com