watch out for that cigarette butt!
July 29, 2008 8:23 AM   Subscribe

Hypothetical Filter: Would someone be able to throw a cigarette out of their window and catch my car on fire?

Someone recently tossed a cigarette butt and it bounced off my windshield. I have been pondering a possible situation involving my car catching on fire while driving ever since. I have had a constant oil leak in my car caused by an engine seal. I have had a gas leak in my car to the point where there was a half gallon puddle behind my parked car with a full tank. (I soon realized that a half tank of gas didn't leak; it has since been fixed.) Still I knew there would be fumes beneith my car that could cause a fire.

Outside of the dangers of the flame starting from within the car or by another part of the car, what are other instances (such as a cigarette) that could cause my car to become engulfed in flames on the road?
posted by thetenthstory to Travel & Transportation (28 answers total) 2 users marked this as a favorite
Easy. You have an open window or sunroof, and the butt comes into your car and lands on a pile of clothes in the back.
posted by tinkertown at 8:28 AM on July 29, 2008

Mythbusters tested this and dropped a lit cigarette into a pool of gas and couldn't get ignition.

Honestly, if your car is in motion, it's virtually impossible that a lit cigarette would ignore anything on your car. The tiny amount of inflammable substance plus the lack of open flame plus the small size of the cigarette adds up to zero. It's much more likely you'll just be killed by a fiery car accident.
posted by smackfu at 8:36 AM on July 29, 2008 [1 favorite]

About a year ago some anonymous asshole flicked a cigarette into my car via my open window. The cigarette landed between my back and the seat. I smelled smoke. My coat was on fire. I mean, yeah it was a really cool coat and was very stylish and hot, but when I say it was on fire I mean the kind of fire with flames. Flames that are hot. I pulled over (really quickly, as you can imagine) and jumped out and the back of my coat was covered with flames and so was the seat. I yanked off my coat and used it to beat the seat and got back in, super pissed off and minus one hot coat. I didn't know about the cigarette until I saw the still smoldering butt laying on my seat.

what are other instances (such as a cigarette) that could cause my car to become engulfed in flames on the road?

Wipe off the area around your gas tank after filling it. No sense giving wayward cigarettes something to look forward to.
posted by iconomy at 8:36 AM on July 29, 2008 [7 favorites]

Well, there´s always the classic horrible fiery car crash. That´s actually pretty rare, but you could crash your car into something that´s already on fire.

Driving over fireworks being set off can´t be good.
posted by yohko at 8:39 AM on July 29, 2008

Mythbusters kind of tested this myth- they only tested directly lighting a trail of gas.

"If the trail of gas from the leaking gas tank of a moving vehicle is lit, the fire can catch up to the tank and blow up the car.


Through small scale tests, the MythBusters discovered that gas burns at just over 3 miles per hour, which is as fast as a brisk walk. Next, they lit leaking gas trails from both a remote control car and a regular pickup, and the flame did not catch up to either. A car going at the low speed of 20 miles per hour could easily outrun the stream of fire. Finally, they let the gas catch up to the tank, and it did not explode. In order to create an explosion, the Mythbusters filled the tank with enough gasoline to get an ideal fuel/air mixture for combustion. Even so, they could not make the gas tank explode so this myth was completely busted."
posted by kidsleepy at 8:40 AM on July 29, 2008

Mythbusters tackled the gas/cig question and found someone basically needed to be smoking the cig for it to be hot enough to catch gas on fire. The flashpoint of oil seems to be about 100F less, but the same probably holds true. Factor in how little of gas or oil is contained in the bit leaking from your car at *any one time* and it's very unlikely those will do it. I know the cig is being thrown out of a moving car, but that's air blowing on it, not through it. Only the periphery will get the extra oxygen rather than the whole thing, so I don't think that's a concern either.

Open window, clothes on the floor as tinkertown said? Probable. I've even had someone flick a cig out of their car and land on mine and catch on the windshield wipers. It discolored the glass and I'm sure would have melted the plastic if it'd been closer to it, but that's about the max damage without the through the window theory. I'd be worried if I had a convertible.
posted by jwells at 8:43 AM on July 29, 2008

tinkertown has the right idea. A pile of cloths (especially cotton) that a lit cig lands on top of would smolder for awhile and eventually (potentially) ignite. The is probably the most likely scenario. I wouldn't be so concerned about your oil and gas fumes. Although both are ignitable and are fire accelerators, they take quite a bit of energy as well as the right oxygen mixture in order to ignite.

I haven't seen the mythbusters where they tackle the gas/cig question... the thing about gas is, the liquid is hard to ignite due to the lack of oxygen...but the fumes are ignitable. If a lit cig is held above some gas fumes there is a potential for ignition. However, there would have to a concentration of fumes in just the right oxygen mixture for this to work. A moving vehicle would most likely not accumulate fumes very easily.
posted by nickerbocker at 8:51 AM on July 29, 2008

This is one of those things that likely won't happen ... but given enough cigarettes and enough people and enough gasoline ... something, somewhere will happen. It's a freaky world.
posted by Cool Papa Bell at 8:52 AM on July 29, 2008

I flicked a butt out the window once and -- serves me right -- it came back in the open rear window and somehow got sucked under the plastic molding into the rear hatch area, where it smoldered in the insulation. I didn't realize it until I smelled smoke, then my eyes started tearing, and I pulled over. Luckily I had a screwdriver in the glovebox so I quickly detached the molding and tamped it out. If I hadn't gotten to it quickly I do believe my car would have gone up in flames, because it was starting to spread. Just another reason I'm glad I quit.
posted by Camofrog at 9:01 AM on July 29, 2008 [2 favorites]

I've had stuff thrown through my sunroof a couple of times. I don't see why a cigarette couldn't be. Your real risk is your upholstery, I imagine, (unless it's fire-retardent like home upholstery has to be), or stuff on your seat.
posted by dowcrag at 9:03 AM on July 29, 2008

Just last night I watched a documentary on TV suggesting a thrown cigarette as the cause of the 1999 fire in the Mont Blanc Tunnel. Evidence suggests that a spark or thrown cigarette was sucked in at a truck's air intake, setting the air filter on fire, although this is impossible to prove conclusively.
posted by ghost of a past number at 9:09 AM on July 29, 2008 [1 favorite]

The flashpoint of oil seems to be about 100F less, but the same probably holds true.

One thing worth adding is that both gas and oil ignite much more easily if contaminates are added. For example, the King's Cross fire was caused by a lit match igniting grease that had become contaminated with debry over time. Trying to light gas or oil by itself is similar to trying to light candle wax by itself, whereas if other materials are present they can act as a wick.
posted by burnmp3s at 9:11 AM on July 29, 2008

A lit cigarette could land in upholstery and smolder for quite a while. It might not be common, but cigarettes are responsible for a lot of fires, so it clearly happens. A lit cigarette in leaves under a parked car might ignite the leaves. Oily rags are another good ignition option, and not uncommon in a car.
posted by theora55 at 9:35 AM on July 29, 2008

A few years ago, I recall a local news story about a guy lighting his own car on fire with a poorly aimed cigarette.

Hah, here's the link.
posted by jamaro at 9:54 AM on July 29, 2008

Not cigarette-related, but years ago I recall my dad warning me about the dangers of parking my (then new-fangled) catalytic converter-equipped car on or near dry grass lest the hot converter start a grass fire which would engulf my car. Being a snotty teen, I scoffed at his advice back then so I'm rather embarrassed to admit today that googling "catalytic converter grass fire" returned a significant number of positive hits.

Ack, sorry for doubting you, dad.
posted by jamaro at 9:59 AM on July 29, 2008

No, if your car is moving heck no, if your car is moving and had recently been doused with gas, still unlikely.

Like dowcrag said, your real danger is in the interior.
posted by TeachTheDead at 10:08 AM on July 29, 2008

While not explicitly fire-related, cigarettes are a major annoyance for motorcyclists. It's pretty easy to conceive of a scenario where a flicked butt could cause a fatal accident. I wish I had a nickel for every butt that's been flung my way. No mishaps so far, but I have friends who've gotten them in the faceshield and the lap. Given motorists' proclivity to not see bikes (inattention blindness), it's just a bad idea to fling a lit cigarette. Or any cigarette. Safety concerns aside, litter ain't cool.
posted by Eideteker at 10:26 AM on July 29, 2008 [1 favorite]

Did this to myself when I was a kid. Flicked a cigarette out the window as I was driving, but didn't notice that the wind blew it right back in. It landed, as I discovered about ten minutes later, in a fold in the right cuff of my jeans. I was driving on a rural freeway on a hot summer day, so when I smelled smoke, I just assumed someone was slash burning, and rolled up the windows. At which point the car filled with smoke. Freaked out, I rolled the windows back down and tried to figure out what was going on. Eventually, I noticed that the whole back of my right pants-leg had completely charred away from the knee down. There was no shoulder on the highway, so all I could do was stomp on the back of my leg with one foot and head for the closest exit. Later, I tied a bandana around what was left of my pants-leg and went on with my business, which as best as I can remember, involved going to see a girl.
posted by It's Raining Florence Henderson at 11:47 AM on July 29, 2008

Not a car, but somebody once flicked a cigarette butt on a canvas tarp covering a boat my dad owned. It landed on the area of the tarp that was right over the gas tank [which was not very fume-proof]. Instant, dramatic ignition was the result. That could have happened while it was being towed, I'm sure, because: flick, wooooof! fire!
posted by Acari at 12:40 PM on July 29, 2008

smackfu writes "Mythbusters tested this and dropped a lit cigarette into a pool of gas and couldn't get ignition."

This is because contrary to popular belief liquid gas really ain't all that flammable. You need to mix it with oxygen/air. The dust bunnies/take out napkins under the seat fanned by the brisk breeze of an open window are though.
posted by Mitheral at 12:49 PM on July 29, 2008

I've had tossed cigarettes find themselves lodged in the crack where my convertible top meets the body work. I attribute it to the aerodynamic flow of air around my car. It doesn't set the car on fire, but they have left some burn marks.
posted by Civil_Disobedient at 3:06 AM on July 30, 2008

The summer the IKEA opened, someone was transporting a mattress home on top of their car. Mattress + cigarette = no mattress. So it seems not to be a problem of the car itself, so much as open cars often allow access to flammable materials.
posted by Weighted Companion Cube at 5:24 AM on July 30, 2008

Don't idle on dry leaves. (Your SUV may catch fire and explode). 1, 2
posted by acro at 8:56 PM on July 31, 2008

Don't idle on dry leaves. (Your SUV may catch fire and explode).

I was just going to ask about that scene. Can that really happen?
posted by bukharin at 10:25 AM on August 2, 2008

I've twice seen grass fires started by hot exhaust on rally cars.
posted by Mitheral at 11:27 AM on August 2, 2008

Throwing a lit butt out the window and catching a car on fire anecdote:

Late winter 1975, Rome. Two unwelcome -and penniless- guests, Dan and Phil, both dimwitted exes of a former friend, had abruptly foisted themselves on me, while I was staying in a rented room in 84 year old Signora Savignano's apartment. They had stolen gas by siphoning it from parked cars with a rubber tube, as they drove down from London and didn't have money for food, or anything except cigarettes.

As we sat eating lunch in the living room, Phil flicked his lit butt out the window. I pointed out to him that this was inconsiderate and leaned over the balcony to see if the butt had landed on anyone. It had landed on the roof of a convertible car below and was, incredibly, rapidly burning a hole in the canvas. I yelled out to the guys to help me and we ran a sort of fireman's brigade chain, throwing pitchers of water onto the car, aiming badly for the roof, until the burning had stopped. They thought this was hilarious.

A half hour later the doorbell rang. It was a police officer, carabinieri, with the disgruntled owner of the car. I had to fork over thousands of lire (not easy for 21 year old me on a really tight and limited budget) to repair the car roof and in addition to pay a fine for throwing water off a balcony, which is, apparently (some modern version of the Dejecti Effusive Act), against the law in Rome.
posted by nickyskye at 5:15 PM on August 4, 2008 [3 favorites]

Response by poster: Thanks for all of the posts. I am going to conclude that the easiest ways for your car to catch fire:

1. Have a cigarette somehow land in the wrong place. Most likely in your car or on your convertable top.
2. Idle your car on dry grass.
posted by thetenthstory at 12:27 PM on August 7, 2008

Sort of related, an attorney at the office where I work just came in and said that while he was driving, someone threw a cigarette out of their car, IT LANDED IN THE POCKET OF THE SHIRT HE WAS WEARING, burning the shirt and him.
posted by Lucinda at 10:19 AM on September 18, 2008

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