I was reading how a major blaze in Ocean City, MD was traced to a cigarette butt flicked out a window. How do investigators determine this with such pinpoint accuracy?
There are a lot of different techniques employed. Fires tend to burn up, so something like a burned electrical outlet may produce a V-shape char pattern up the wall. In an outdoor fire, you could do some backtracking based on wind direction to narrow down the point of origin. Sometimes you can find physical or chemical traces of whatever started the blaze (though I’d wonder if anything in a cigarette would survive) and there are often chemical changes that vary based on the heat of the fire at a particular place. There might even be an eye witness or a confession.
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And when all else fails, it’s usually ruled as electrical.
When all else fails, the fire is supposed to be ruled as “undetermined.” It is a perfectly valid cause, just not as sexy as the other choices. I’ve had investigators call fires electrical in buildings with no electric service. Go figure.
The basic, overriding method for determining the cause and origin of a fire is to work from unburned to most burned areas. The area of origin will have burnt the longest, since that’s where it was going first. The most amount of damage will be there*. Once you’re in the area of origin, now you start to look for indicators of how the fire got going. Most of the time, there is a V pattern that points to the origin (or it can point to a drop-down from a fire’s normal spread, which stinks) Is there an electrical component nearby that may have malfunctioned? There’s a whole branch of fire investigation that looks at failed electrical components to determine if they caused the fire, or if the fire caused an electrical failure. Are there other heat sources nearby, such as an ashtray or heating system component? What did the occupant say was there to start with? Is there a pour pattern on the floor when an accelerant was used? Did the accelerant detection dog hit on something that shouldn’t be there?
Brush fires are usually easy to determine - they burn in a very distinct V pattern away from the origin, uphill, and with the wind. Go back to the point of the V and something will usually be there to tell you what started the fire. About ten years ago, a very, very large mill burned down in the city nearby. The news had said the fire was caused by carelessly discarded smoking materials on a nearby highway. My first reaction was to call it bull, but I know the investigator very well. In fact, he’s one of the three people to really teach me how to investigate fires. If he said it was a cigarette, then gosh darn, it was a cigarette.
The reference used for fire investigation is NFPA 921, Guide for Fire and Explosion Investigations. Lots of reading, but it’s most of what you need to know to do the job correctly.
*Barring any strange fire behavior - storage of combustibles, high winds/HVAC, interior finishes, etc
Happens a lot out in forests, too, where the trees have no electrical service.
I think they also call it a ‘lightning strike’.
From what you post, I will make an assumption that this was a fire with an origin of wildfire(outdoor, forest, etc.)
The ember on a cigarette is every bit as hot as any other class A ember. When it comes into contact with another class A material witch usually has an auto ignition temp of just over 400 deg. (F) it will in many situations cause the other material to begin to burn(oxidize) rapidly enough to cause light.(a little wind causes this to be more efficient) The fire in such an area usually burns all combustible materials rapidly leaving the remains of the cigarette that is treated with chemicals to inhibit combustion at normal oxygen air ratios easy to find. Then by burn patterns that are easy to follow, Bingo! The source is found.
There are four causes of fires; incendiary, accidental, natural, and undetermined. Electrical fires caused by utility-style electricity are ruled as accidental fires (unless you rewired your toaster to burn your kitchen down, then it’s incendiary).
Lightning is a natural cause, not accidental.