Built on Facts

Fire Drill!

[I’m foregoing the usual Saturday miscellany for a Very Special Built on Facts. It’s important!]

Imagine a basketball sitting on the top of a hill. The slope of the hill is pretty gentle, and so you can roll the ball around a bit without the risk of it rolling away. But hit it too hard and it’s going to catch the slope and zoom off. You and many of the materials which surround you are not so different. They’re made of atoms which are comfortable so long as you don’t hit them very hard. But hit them hard enough with oxygen molecules and they’ll go flying away. And they’ll hit other molecules and send them flying away attached to atmospheric oxygen too.

We call this fire.

Today got approval to buy some anhydrous ethanol for some more stinky pyridine measurements, and almost no sooner had I walked out of the office when the fire alarm sounded. The office is on the 4th floor and I was already headed out, so I adjusted my trajectory a bit from the elevator to the stairs. From the time the alarm sounded to the time I was outside was about 20 seconds. I like my molecules where they are.

So do most people, but unfortunately most people’s response to fire alarms is pretty lax. People look around and dither, and watch other people look around and dither. We’re herd creatures and so stasis breeds stasis. Then they stand around some more to wait for smoke, and eventually they start to leave. If they’re lucky they can. If they’re not then exits might be blocked by fire or stampeding crowds, assuming they haven’t already succumbed to heat or smoke. Fire requires heat energy, and that energy builds up rapidly in a burning building. The growth is exponential – it can’t escape to the outside and so it’s absorbed by ts surroundings, setting them on fire. Which produces more heat, growing the cycle. The exponential function grows shockingly fast, and so do building fires. If you want to see some truly harrowing footage look for the video of The Station nightclub fire. I’m not directly linking the video because it’s pretty disturbing. I do recommend watching this video reproducing the event under controlled conditions.

From ignition to everyone still inside being dead takes about 90 seconds. And most of those 90 seconds are before matters look serious – by the time black smoke starts billowing escape would be nearly impossible. New buildings with sprinklers and fire-resistant materials can extend this time considerably, but as a rule you should assume you have 90 seconds to be outside or dead. That’s a minute and a half; it’s plenty of time for calm and measured action. You don’t have to run or panic but you do need to get out. If you wait, by the time the situation is obviously serious you may have already sealed your own fate.

Pay attention to emergency exits too. Few people do, and it’s to their detriment. Numerous observations have demonstrated that people tend to automatically leave by the door they entered, even if there are other doors closer. Knowing this you can avoid the instinct.

You might be able to tell that I was raised by a fire investigator. Well, I haven’t died in a fire yet. If you pay attention during fire drills (and keep your smoke detectors functioning at home), you probably won’t either!


  1. #1 Dad
    January 31, 2009

    Well said! I’m glad you were paying attention. I hope your brother and sister were too. I also hope your reader listen. Love, Dad

  2. #2 Uncle Al
    January 31, 2009

    Leave a fire situation on your belly. Air, being transparent, is a terrible blackbody radiator. Standing up into 1000 C air voids the manufacturer’s warranty. Touch a closed door before opening. If the door is warm to the touch there’s a skeletal guy with a scythe waiting on the other side.

    Move fire extinguishers from doorways toward the center of the lab. You don’t fight your way in to save the lab, you fight your way out to save yourself. Replace metal fire extinguisher pins with plastic pins. If you squeeze before pulling with plastic, no biggie. If you squeeze before pulling with metal, no fire extinguisher.

    There is little a Metal-X extinguisher does that a bucket of builder’s dry sand won’t. Give the bucket a labeled paper cap to shut up the Safety Committee.

  3. #3 Nemo
    January 31, 2009

    “New buildings with sprinklers and fire-resistant materials can extend this time considerably”

    Actually, it is almost impossible to die from a fire in a building with a functioning sprinkler system. The exceptions involve explosions and broken sprinkler systems. They really are that effective.

    See http://wiki.csinet.org/index.php?title=Fire_Sprinkler_Systems for instance.

  4. #4 CCPhysicist
    January 31, 2009

    Lots of good points. That simulation should be part of our safety presentation in the lab, since students just don’t seem to get the idea that fire happens fast. Does Uncle Al have any stories from the chemistry lab?

    Interesting point about fire extinguishers. It would appear that Code requires ours to be by the door, and ditto for the fire blanket. That does have the advantage of always being in a predictable location so you don’t have to look around for them.

  5. #5 Matt Springer
    January 31, 2009

    Right about the sprinkers, but like any safety device you shouldn’t trust your life to them if you can avoid it. You never know if they might malfunction or fail if the cause of the fire happens to break the piping system.

  6. #6 MikeB
    February 1, 2009

    Excellent post, and one which every lab and hospital should have on their notice board. I worked in a hospital for a while, in a department which (amoungst many other things) organised annual fire lectures and were part of the fire team.

    Everyone had an excuse for not going to the lectures (which were pretty good),even though it was mandatory, and would often refuse to get out when the alarms went off, because they were doing something ‘important’.

    About two years ago, they had a big fire (no casualties, fortunately) – hopefully everyone now understands why knowing what to do in a fire is important, and why getting out fast is how you stay alive.

  7. #7 Art
    February 1, 2009

    When selecting smoke detectors be aware there are two basic types, ionization and photoelectric, and that each has strength and weaknesses.

    The most common, and cheapest, are the ionization type. They use a tiny radioactive source to measure the presence of the products of an open and active flame. they are great at detecting the sort of leaping flames you see in movies when they show a fire. They don’t won’t work well at detecting slow, low smoldering fires.

    The sort that produce great quantities of dense smoke, carbon monoxide and toxic gasses. The sort that is most common in residential settings.

    The photoelectric type are usually a little more expensive. They detect changes in the ability of the air to transmit light. Smoke blocks light so they detect smoke. They don’t detect the transparent combustion products of an active flame very well.

    The ideal situation would be to have both types present. There are a few models that combine both in one package. Barring that sort, and given a choice of only one type of the two, I would go with the photoelectric.

    When buying the smoke detectors it isn’t always clear which type is which. Ionization type don’t often tell you the method used in detecting the ‘smoke’. A clue as to which is which is that the ionization type will have a NRC warning label because of the tiny radiation source. If it has a NRC warning it is, or contains , an ionization unit.

    Photoelectric types are more often clearly labeled as to the type and method used, often to justify their increased cost, and they will lack the NRC warning.

    Smoke detectors need to be both outside and inside sleeping areas, between likely sources of fire and the sleeping areas and at least one of each type on each floor. Ideally they are all connected so that if one goes off they all do. The sound of six or seven smoke detectors sounding off at once will pretty much raise the dead. It will wake you and the neighbors up. A good thing.

  8. #8 Carl Brannen
    February 2, 2009

    I’m surprised that 3/4 of the participants in that bad idea managed to survive it.

    The problem with Uncle Al’s advice to leave a fire on your belly is that you could get trampled.

  9. #9 Casz
    February 2, 2009

    An important factor when you are discussing fire drills is to practice going to your congregation point. As you say, the herd instinct is very strong and if you don’t practice going to your assembly point, one of your group may re-enter a dangerous situation because you went with the herd instead of to the agreed place.

    More difficult to do at a club but you could all agree to exit doors.

  10. #10 Dave
    February 5, 2009

    I have to say I’ve been guilty of dithering a few times, although it is not purely out of a herd mentality; it’s because I’ve been lied to so many times by fire alarms.

    I know the only thing to do is to take it seriously, but after going through dozens of false alarms and unannounced drills, I sometimes struggle to respond appropriately.

    I can think of a few things to help in some situations, but ultimately I’m not sure what can be done about this; there’s a bit of a “boy who cried wolf” factor to fire alarms, and I can sympathize with people who don’t respond right away to an alarm in a building they’ve heard a number of times before. It’s human.

    Thanks for encouraging me to do the right thing though (those videos ARE surprising).

  11. #11 First Alert sc9120b
    November 2, 2010

    This was a very interesting read. It is so true that we are herd creatures and our response time in a building fire is too relaxed.

    The thing that most people don’t realize is that when you are in a confined space like a building, it’s rarely the fire that kills people, but the smoke inhalation.

    Fascinating post, I look forward to reading more from you.

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