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Mall on Fire

Science of Fiction Q&A

Happy Birthday, America! This week in the Science of Fiction, we’re going to celebrate your founding in the traditional way, by blowing things up and starting fires!

Question from JLeaff:

“What is the best way to set a large two-story mall on fire using only gasoline and matches? My character steals gasoline by breaking into gas stations and stores them in containers over the course of a few days to a week. They plan to set an entire mall on fire, trapping and killing everyone in it. What is the best way to pour the gasoline so the mall bursts into flames? What is the least amount they need to do that? And does this plan even make sense in the first place?

“Note: okay, I might as well admit I’m writing a Hunger Games fanfiction. This character has no laws stopping them from breaking into the station or setting it on fire in the first place since it all happens in the games.”

This could be pretty challenging. There are a lot of factors fighting against you. Also, I appreciate the clarification that this is for fiction and I’m not giving actual advice on large-scale arson.

First, let us consider what fire needs to burn: heat, fuel, and oxygen.

Malls have lots of the last one. They have big open spaces with lots of airflow. An individual store might have a lot of fuel; books and most clothing will burn pretty well, even moreso with the encouragement of gasoline.

Gasoline, for its part, is a fine accelerant. It’s very easy to light, and burns very hot. It will definitely get your fire going. It will not, however, keep your fire going. Gasoline burns hot and fast. That’s what makes it a good fuel for cars. So while it will get your fire started, it will burn away pretty quickly. The thinner you spread it, the faster it goes. Just something to keep in mind.

This makes it sound easy to burn down a mall, but there are some challenges you’ll face, mostly relating to building practices.

Most of the fuel in malls is concentrated into fairly small concrete boxes we call stores. Most fires in malls are contained to one or two stores just by the nature of the architecture. Concrete doesn’t transfer heat very quickly, and it does not burn, itself. Spark up an H&M and you probably won’t even singe pages in the Barnes & Noble next door. In addition, the big empty hallways with ceramic tile flooring create fireproof divides between stores that make it difficult for fire to spread.

This isn’t any kind of coincidence. Mall fires can be terrible if not contained. They’re both potentially very fatal, and also very expensive. The latter makes building owners very keen to see that it doesn’t happen, so building codes for decades have worked to make it all but impossible to burn down a whole mall.

The concrete and glass everywhere aren’t only used because it’s cheap and easy to work with, it’s also very fire resistant. The wide, empty ceramic hallways don’t just exist for ease of walking, they’re specifically sized to prevent fires from spreading and make it easier for people to escape if there is a fire. Even the doors are all designed to let people escape a fire, always opening outward and having no interior lock. To make matters worse, malls all have fire suppression systems. There are sprinklers all over which will spray enough water to put out most fires. If your mall follows anything like a modern building code, actually burning it down would be incredibly difficult.

However, I’m not here to naysay. I’m here to help you find solutions.

If your real goal is creating life-threatening danger for the people in your frustratingly flame-retardant mall, there are definitely options.

The first is department stores.

While the smaller shops are well-contained boxes with limited fuel and easy egress, large department stores are typically huge expanses of flammable material with few exits. The fuel is laid out almost ideally: clothes hanging close to each other, but not so densely that air cannot flow around them. If you can get some people inside a department store, and then use your gasoline to light fires at every exit, you could easily trap a number of people in a blazing death trap. Houray!

Next, consider the dangers of smoking.

Most death in fires comes from smoke and gas inhalation rather than burning. Humans need to breathe relatively cool oxygenated air. Burning things have a bad habit of converting that kind of air into very hot, oxygen-free gases. Depending what you’re burning, that can also be very toxic. A couple lung-fulls of the smoke let off by burning polyester or nylon could scorch someone’s lungs, suffocate them, and poison them all at the same time besides. Pick your most plastic-filled stores, set them ablaze, and just poison everyone who breathes it to varying degrees. Joy!

Also, think about an older building. Old buildings that included wood and brick in their construction are much more flammable. Those are few and far between nowadays, and likely even less common in the concrete misery of the Hunger Games setting, but the definitely existed and were absolute death-traps if they sparked up. The carpets burned, the walls burned, the ceilings burned. All of it, a conflagration of terrible choices. What an opportunity!

Finally, consider undermining the existing safety systems. You say your character has access to gasoline from a gas station. Do they also have access to the Mall’s utility rooms?

What would happen if you drained the water from the sprinkler system and replaced it with gasoline?

A typical gas station will have tens of thousands of gallons of gasoline, probably enough to fill your sprinkler system.

Normally, the pressure to the system would be provided by the town water main. If you still have running water, then that should work fine. You don’t have to worry too much about water coming in after the gasoline. It will eventually put out the fire, but initially it would just help spread it around as the gasoline would float on the water and keep burning.

If your water isn’t running, there is sometimes a pump associated with a sprinkler system. You could even just connect that pump straight to the gasoline reservoir with a hose and save lugging jerrycans back and forth.

So far as starting the fire, sprinklers are set off individually by a small glass bulb in them being heated. Once you crack that bulb, the water (or gasoline) start flowing. If you spark up the flowing fuel from one sprinkler, that fire should set off the surrounding sprinklers setting off a chain reaction of fiery death. Glorious!

Thank you for the question. I haven’t speculated this much about arson in… well ever.

Are you an amateur writer looking for science advice on your project? Email the contact form and include “Science of Ficetion” in the subject line. We can’t promise we’ll be able to answer all questions, but we will at least let you know if we can. 

“IMG_7157”by curiouslee is licensed under CC BY 2.0

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Ryan

Ryan is a professional nerd, teaching engineering in the frozen north. Somewhat less professionally, he is a costumer, author, blacksmith, juggler, gamer, serial enthusiast, and supporter of the Oxford comma. He can be found on twitter and instagram @studentofwhim. If you like what I do here, feel free to leave a tip in my tipjar.

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2 Comments

  1. Bricks don’t burn! Asphalt roofs, on the other hand, are very flammable. I think that’s what’s burning in the picture at top.

    If the gas station was next door to the mall, or in the mall parking lot, maybe you could run a hose (with a pump) from the station’s storage tank into the mall’s sprinkler system. If it was a dry-pipe system, there wouldn’t be a lot of standing water in the pipes that would get sprayed on the fire before the gas started flowing. Or you could dump the water on the ground outside the mall and replace it with gasoline. (This would never work in real life. Any sort of security system or surveillance would detect this before you got started, but in the context of the story, maybe there wouldn’t be one.)

    You can also do a lot of property damage just by setting off the sprinkler system, even if there is no fire. Getting all the sprinklers to activate at the same time would be hard. I doubt anyone would drown, if mass murder is your goal.

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