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Arson Science Rewritten
An anonymous reader handed us a link to an AP story about advances in the science of arson investigation. Many assumptions about fire, long held by investigators, have been overturned in recent years as scientists have come to understand concepts like 'flashover'. The repercussions of these findings is having an effect not unlike the use of DNA in crime-solving; people are being set free, and old cases are being re-examined. From the article: "Significantly, flashover can create very hot and very fast-moving fires. And it can occur within just a few minutes, dashing the concept that only arson fires fueled by accelerants can quickly rage out of control. The studies began to chip away at the old beliefs -- critics call them myths -- but it took years. Through the 1980s, texts at the National Fire Academy in Emmitsburg, Md., still taught the traditional techniques. It wasn't until 1992, when a guide to fire investigations by the National Fire Protection Association -- 'NFPA921: Guide for Fire and Explosion Investigations' -- clearly laid out, in a document relied upon by authorities nationwide, that the earlier beliefs were wrong."
you would be skeptical about the need for "accelerants". If you've ever seen a fire move through a room, it can go from a small area to engulfing the entire thing in less than a minute without any help from gasoline etc. I'm pretty sure that what happens is that the heat from the small fire vaporizes ordinary non-volatile things, like household furnishings or materials, and those vapors then act as the accelerant.
I know there was a case a few years ago where an "arsonist" in TX was executed for having killed his family, and within less than a year it was established that he was innocent.
I'll just say, the idea of someone being executed based on expert testimony from arson investigators, who are not even scientists, is appalling. Experts are only right until some new piece of knowledge comes along and changes the field.
I used to be a volunteer firefighter and also served as a fire investigator. My experience began around 1981 or so; later (late 90s), I worked for a Police Department doing crime scene work and part of that was fire investigation.
From TFA:
Up until the 1990s, this is what fire investigators were taught:
Fires always burn up, not down.
I was NEVER taught that; just the opposite. Fires tend to burn up FASTER than they burn down, but geez, anyone who has ever actually WATCHED a fire burn knows this statement is nonsense.
Fires that burn very fast are fueled by accelerants; "normal" fires burn slowly.
I was NEVER taught that; just the opposite. We were taught that accelerates were ONE WAY a fire MIGHT burn faster than you would expect under similar conditions. We were also taught that is EXTREMELY difficult to gauge how fast a fire "should have" burned. I did my first chemical test on fire debris in 1986 using GC/MS via a very simple headspace analysis on a sample that the state lab sent back as negative (my test was positive for something, perhaps ambient artifacts, but was an educational run, not an 'official' test). With the negative test result, we sure did not try to use evidence of 'how fast that fired burned' to assert the presence of an accelerant.
Arsons fueled by accelerants burn hotter than "normal" fires.
Somebody is oversimplifying the concept of "fire load" here. There are a WHOLE LOT of things than can make a fire burn hotter than 'normal.' In fact, as a common theme I am trying to represent, "normal" is not a well defined term for real-world fires. Rural firefighters and investigators certainly knew this before 1992.
In fact, this statement glosses over another issue about arson - they often, quite often, don't involve 'accelerants' at all.
The clues to arson are clear. Burn holes on the floor indicate multiple points of origin. Finely cracked glass (called "crazed glass") proves a hotter-than-normal fire. So does the collapse of the springs in bedding or furniture, and the appearance of large blisters on charred wood, known as "alligatoring."
The clues to arson are clear?? Man, I clearly remember in the early 1980's being taught exactly the OPPOSITE of what this article says was the "norm" back then. Perhaps it was taught somewhere, but not in RURAL North Carolina. Absolutely NONE of these "clues" are evidence of arson - only of certain fire conditions.
What we were taught in our arson investigation classes, and what I came to learn through experience, is that arson was/is and EXTREMELY difficult crime to prove. That means it is difficult to prove that a fire was arson, much less who did it.
Truthfully, based on my experience, I don't see the point of this article. It asserts 'beliefs' about fire investigation pre-1992 that just are not true.
And finally, the article gives the tragic story of the Lee family that occured in 1989. While presenting NONE of the evidence that was used to convict him, the story creates the straw man that just because it was 1989 and fire investigation changed (around then, according to the article), he must be framed. I don't know of his guilt or innocence, but that's a might big leap of logic.
Computational Chemistry products and services.
Sad thing is, mansonry conducts heat. While some regions might not consider this a problem, try living in a brick house when the temperature drops below 0 farenheight. It can't be fun, so the solution is to build a brick exterior and set up a wooden insulated studwall on the interior.
Besides, what is going to hold up your concrete second floor? Or is it that all houses in your country have no cellars or second floors? The cost of constructing a house made entirely of mortar, brick, and stone is immense. Thus, wooden houses.
In the ideal world, nothing burns. In the real world, even concrete and steel give under fire.
In the ideal world, concrete and metal buildings are as inexpensive as wood. In the real world, this just isn't so.
In Mother Russia, the concrete burns you!
-jbevren
that this thread will turn into a flame war.
My script don't crash! She crashes, you crashed her!
Tried reading the article but my Sony laptop caught on fire.
Pretty much all (Western and Eastern) European home construction is concrete / brick based and this extends through most of Russia and large parts of the rest of the world. Building out of wood is a foreign concept for a large number of people in the world. Many countries don't exactly have huge forests either - nothing like what we enjoy in North America.
;)
Basically Europe is completely deforested. There are forests, sure, but they would be gone pretty quickly if people started building homes out of wood.
As for the engineering aspects - concrete is strong and you can easily drop a concrete slab as the floor on your second story if you use walls of reasonable thickness - or you can use wood flooring suspended on a central beam(s) or one of dozens of other ways that builders use to suspend a floor in a wood house. Very few houses in Europe are only 1 story.
I've seen pre-fabed buildings being put together (and quickly) in Poland and Eastern Europe using both methods - a crane, a few hours and a welder is all it takes to get the structure done since the buildings come on the truck with rebar in place, holes and supports already in the concrete. Pretty cool actually.
Assembling a house out of brick isn't terribly difficult either - many people in Eastern Europe build their own houses, by hand, slowly, after they come back from their day jobs or whatever. Try doing that with wood construction and you'll end up with a crooked house that falls down in a year.
There is also a newer technology under the category of "insulated concrete forms" (ICF) - basically big hollow styrofoam blocks that you assemble like legos and fill with concrete (they have internal structure and rebar holding them together)
A house built with ICF has superior insulating properties (and does a fair job of blocking wifi signals too
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After something like 40 years of this being accepted, someone actually tested it. Result: no freaking correlation at all. The variation in composition of bullets within a given box was the same as variation among bullets from different boxes, purchased years apart. This is a completely worthless forensic technique.
Or consider early DNA testing. Up until at least the mid '90s (I don't know what they do now) a DNA test only looked for matches at a small number of base pairs. For any given DNA sample tested, there would be thousands of people in the world that matches that sample. What this meant was the the scientifically correct way to use DNA testing was to find your suspects using traditional police techniques, and THEN use a DNA test. If you had, say, 3 good suspects, and one of them had a DNA match, then that was very good evidence against that suspect. Unfortunately, sometimes it was used the other way. They'd start with the DNA, match it against whatever samples they had on file, and if they got a match, they'd go after that person. That's bogus.
If you look into the science behind much police investigation, you get this strange feeling you've fallen through some kind of wormhole and gone back to the early 19th century. It's amazing how much in common use has not been rigorously tested and peer reviewed by real scientists.
Many of you across the pond won't be familiar with this disaster, but it's as good an example of fire spreading quickly without accelerants as you'll ever see. It all started when someone dropped a cigarette, and within a few minutes a hundred-metre long wooden stand was a goner, killing dozens of people. There's a video of it on YouTube, although I should warn you that there's one or two scenes in it which I personally find slightly difficult to watch.
I wonder why my European parents have a wooden house (wooden frame filled with stone wool and covered with wooden planks, built in 1998), why their neighbours save one have also wooden frame houses, the oldest one being from 1654 (yeah, that's more than 350 years ago), why 25% of Germany's area is covered by forests, why Europe is in fact increasing its forest area, why towns like Quedlinburg or Erfurt are declared UNESCO cultural inheritance for their timber frame town centres, where all those pittoresce Black Forest and Bavarian rural houses come from, why we talk about "balconies" (which is just the german word Balken = timber).
Wood is a very common material in residential construction in Germany, and in fact its usage has increased with the larger number of prebuilt houses being built here.