Fighting sprinklered fires
An early morning 911 call alerted the fire department of smoke coming from a large warehouse storing used auto parts. When the fire fighters arrived, they heard a water gong, indicating that the buildings’ sprinklers were working. In addition, they saw white, steamy smoke pushing out around the closed and locked overhead rolling bay doors.
They immediately started cutting the overhead doors with rotary saws to gain entry. Once inside, they encountered heavy moist “cold smoke” from the sprinklers, diminishing visibility inside the warehouse. They then shut off the sprinklers. By shutting off the sprinklers, additional oxygen flowed into the building through the overhead door openings before the fire was actually extinguished, thus bringing the fire back to its free-burning state deep inside the warehouse. Conditions immediately deteriorated, forcing the fire fighters to retreat. A large portion of the roof collapsed, and the fire burned under the collapsed roof for four days while fire fighters tried to remove the roof. The building was a total loss.1
How sprinklers work
Fire sprinkler systems have been around for centuries. Most experts cite Ambrose Godfrey as the inventor of the first successful automated sprinkler system in 1723. He outfitted a barrel with a TNT charge and wick igniter. When the wick was ignited, the TNT blew up the barrel which then dumped the water in the barrel on the fire.2
Wikipedia also says that Leonard da Vinci designed one of the earliest sprinkler systems by automating his patron’s kitchen with a super-oven and a system of conveyor belts. In a comedy of errors, everything went wrong during a huge banquet and a fire broke out. “The sprinkler system worked all too well, causing a flood that washed away all the food and a good part of the kitchen”.3
Today, sprinklers are designed to contain a fire, impede its propagation and intensity, allowing fire fighters time to respond to the fire. In the warehouse case mentioned above, the sprinkler system would have at least contained the fire, but the fire fighters turned off the automatic sprinklers. This combined with the additional oxygen that entered the warehouse when the overhead doors were cut, allowed the fire to continue to burn and result in a total loss.
It’s important to note that sprinklers aren’t triggered by smoke - and they don’t all go on at once. The image of a small amount of smoke triggering all the sprinklers in a building, soaking everyone and everything inside is simply not true. Sprinkler systems are heat activated, one sprinkler head at a time. Most fires require only one or two sprinklers to slow a fire down.
According to a recent study, fires in non-sprinklered facilities averaged an estimated $1.9 million in damages compared to $638,000 in sprinklered facilities. The National Fire Protection Association (NFPA) 2013 report ‘U.S. Experience with Sprinklers” concluded that 48% of reported structure fires indicated some type of sprinkler – wet or dry pipe – present. In the NFPA report, 85% were wet pipe; 12 % were dry pipe; 3% other.