Could all of Salt Lake City burn down in a great, catastrophic fire?

In early February, an unfinished apartment building in Salt Lake City burned to the ground. A month later, a gas explosion leveled two buildings in New York City. And just last week, a 115-year-old building in Des Moines burned up.

But as tragic as all of these fires were, they also all have one thing in common: they didn't expand and burn down most of their respective cities.

That's actually pretty remarkable. In the 1800s, for example, "great" fires ravaged Chicago, Seattle and Vancouver. Much of San Francisco burned after the 1906 fire and New York City has seen enough "great" fires that they're actually numbered. Older cities like London have been radically reshaped over and over by urban fires.

So what changed? Why aren't we seeing massive urban fires anymore? And could a huge blaze come through and destroy a place like Salt Lake City?

Salt Lake City Deputy Fire Marshal Bryon Meyer said it's very unlikely that an urban fire would level a modern place like the core of Salt Lake City. One of the biggest reasons these fires are less common today, Meyer explained, is that the way we've changed the way we construct buildings. When The Great Chicago Fire hit in 1871, most of the buildings in the city were made of wood. They also had highly flammable tar and shingle roofs. In some cases, even the surrounding streets were made of wood.

To make matters worse still, Chicago was using wood water pipes in some areas. When the blaze hit the water distribution network, it left firefighters high and dry. The same thing happened in Seattle, when fire burned the downtown in 1889.

Today most of that has changed. Pipes and streets obviously aren't wood anymore, but buildings themselves are also much more resistant to fire. Meyer said international building and fire codes, which debuted in the late 1990s, require fire-resistant materials. Things like sprinklers also reduce the amount a fire can spread.

Another factor that limits the scope of urban fires today is the fighting techniques. Equipment is standardized so hoses always fit hydrants — something Meyer said wasn't the case in 1871 Chicago — and notification systems have been honed so crews can get to fires within minutes; between fire alarms and emergency dispatchers, blazes don't burn long before crews find out about them.

Meyer pointed to the recent apartment fire as an example of how this works. Though the building itself was a "vertical lumberyard," crews managed to contain the fire because they arrived quickly and took defensive positions around the perimeter. And when flying embers landed on the roof of a nearby grocery store, the building materials meant it didn't immediately burst into flames. In the not-too-distant past — say, 100 years or less — flying embers could have produced a very different fire.

So what would it take to actually burn large parts of an American downtown today?

Meyers said it would have to be something catastrophic. He speculated that a major earthquake could cut off parts of the city, break gas lines and overtax firefighting resources like water and personnel. If that happened, Meyer said, it's conceivable that a major metro center could burn, but it'd have to be a truly catastrophic event.

In the meantime, urban fires likely can be limited. The one caveat: buildings along the urban interface are still at risk from wildfire. Last year, for example, a handful of homes near Park City went up in smoke during the Rockport Fire.

—Jim Dalrymple II

Twitter: @jimmycdii