Reeling from an earthquake, San Francisco once tried blowing up buildings to fight fires
The immediate aftermath of the 1906 earthquake in San Francisco was bleak to say the least. Water mains and gas lines had been ruptured, telegraph lines were broken and 60 different fires were working their way through the city. Even under such grim circumstances, the response to the growing fires was still a bit baffling, and in hindsight, ill advised. In a desperate bid to create a sort of firebreak in the middle of town, hopefully containing the spread of the structure fires, teams opted to employ dynamite to get things under control. The results were nothing to brag about, and yet this was somehow not the last time such a concept has been employed in fire management.
The deployment of explosives was actually initiated early on in the three-day disaster, with a request being sent to artillery troops stationed at Fort Miley only an hour after the quake had struck. They weren’t widely deployed at first though, only being used on buildings that were already on fire for the first day or so. By the second night more ambitions plans for clearing buildings was adopted, with a huge swath of structures being marked for demolition, theoretically to deprive the fires of a clear path across the whole city, similar to the work bulldozers do today when containing forest fires.
The demolition was difficult work at best. Dynamite was carried by hand past flame and sparks into evacuated buildings. Fuses were often supplemented by snatching wiring off of teetering utility poles, all amongst random explosions from burning gas pockets. To make things worse, the explosives used were based on highly flammable black gunpowder, rather than the nitroglycerin usually employed for this level of demolition work. So while many buildings were successfully demolished, there was some contention about whether the explosives helped or hindered efforts to save the city.
Explosions as extinguishers
Based on these events, it’s probably surprising that people are still looking into fighting fires with explosives. The key is that they’re not looking to use dynamite to clear fire breaks, but actually looking at the concussive blast of air that precedes exploded materials to basically blow fires out. Since fires require both fuel and oxygen to burn, a well placed explosion, most likely channeled through a tube of some sort, may be able to push the flames off their fuel, almost like a giant blowing out a candle. This wouldn’t be used everywhere, but may be of use to deal with burning treetops that are otherwise hard to reach with more conventional methods. A similar concept is already used to extinguish burning oil wells, where the shockwave can be contained and focused at a flame, more or less knocking it out.
This method wouldn’t have helped San Francisco very much in 1906, but we’ve learned a lot since then to avoid a repeat of that scenario.
Source: 1906 Earthquake: Fire Fighting, National Park Services