Fire breaks after San Francisco earthquake of 1906

During the fires that followed the San Francisco earthquake of 1906, several mansions were dynamited to create fire breaks. But how would that create a fire break? The materials that the mansions were constructed of were still there to burn.

Odd, I just asked this exact same question in my natural hazards class the other day. Our PhD professor wasn’t too sure of the answer, either. She posited that the buildings were made of masonry exteriors and wood interiors, and somehow reducing it to rubble (possibly if it were controlled to be an implosive blast?) would make it less flammable.

Explosives are typically used in fire fighting by using all of the oxygen in the vicinity in its own explosion, essentially suffocating the fire they’re trying to put out. The fact that what was on fire is made of flammable materials is irrelevant. They use this technique to put out oil well fires, if that’s any indication of it’s effectiveness in extinguishing flames on flammable materials.

I don’t think they exploded buildings that were on fire in San Francisco.

Sorry I didn’t fully grasp the question. If said buildings were not already on fire, I would imagine that rubble in a condensed pile is more difficult to burn than a standing building filled with air. However, in this particular case, the explosives they used actually helped to spread the fire. Hmm. Good call.:stuck_out_tongue:

This is closest, but not exactly right.

Think of the progression of a fire. A fire can creep along the ground, but given an opportunity will rise because of the updrafts it creates. If you have a bonfire you don’t worry as much about the grass surrounding the pile catching on fire as you do other objects farther away having burning embers settle down on them.

In a large street fire, the flames will combine and draw the heat and the embers upward. They’ll jump streets easily and settle on the roofs of the next block. But what happens if the next block isn’t there? The farther the embers have to travel the more time they have to cool to the point where they don’t start new fires. And if they do land on a low-lying pile of rubble, the fires are more easily contained (you can drop a bucket of water on a pile but not on top of a house) and harder to start since you don’t have the super-heated air surrounding them.

Not a perfect solution, but IIRC the fire companies had no water to spray and this gave them more of a chance to control the spread.

There’s quite a bit of information to be gleened from reading full-view books on Google Book search from say 1906-1910. Use words such as “San Francisco” “fire” “dynamite.”

It turns out that using the dynamite wasn’t such a bad idea, except for the fact that the entire water supply of the city was useless because of the earthquake/fire. Evidently, dynamite can be useful only if there is water available to keep down the resulting fire in the material left.

Here’s one book I was reading from an engineering standpoint of commenting on the use of dynamite.

During the Great Boston Fire of 1872, the fire chief of Boston strongly resisted the demoliton of buildings to stop the spread of the fire, as it didn’t work in Chicago the previous year. He ended up succumbing to the political pressures of the city fathers, allowing several buildings to be knocked down with gunpowder.

The gunpowder didn’t work, and only made firefighting more difficult in the building when it did catch fire. Bad idea all around. There’s some good CGI on it from this PBS show.

We still have laws in Massachusetts allowing the fire department to demolish your building to prevent a conflagration, but the city has to reimburse you at fair market value, essentially buying the house by eminent domain without the court costs, or possibility of appeal. Today, you just put water on the exposure building to stop the fire from getting in. A lot easier and cheaper.

Less surface area means less oxygen for combustion.