Myths and Legends
Keep coming back to this page - We will add and change myths every few weeks.
Today there is a plethora of information on the web about almost anything. Just do a search of "thingamajig". Mine came back with a definition and several links to definitions of thingamajig. Its a real word but is it a real "thing"?
Hollywood is one of the best sources of fire investigation myths and legends (along with a lot of other things).
A cigarette tossed into a puddle of gasoline will make everything blow up!
All the evidence burns up! & Ignitable liquids (ie gasoline) burns up completely in a fire.
All the sprinklers go off at the same time.
Every time a car crashes it blows up! (of course only when the director wants it to)
Depth of char / Alligatoring - the bigger and deeper, the faster the fire and more accelerants used
It was a hot, fast fire; they had to use gasoline
Spalled (pitted/chipped) concrete means they used an accelerant
Sagging furniture springs
Patterns on carpet
Cigarettes will light gasoline on fire.
One of the biggest myths in fire investigation surrounds cigarettes. What they will and will not ignite.
Throwing a lit cigarette into a puddle of gasoline will NOT cause the gasoline to ignite (explode in Hollywood hype!). The ATF and several others including the FOCUS team have conducted many experiments trying to get cigarettes to ignite puddles of gasoline. They tried these experiments with idle and active draws on the cigarettes and none would light the gasoline.
Notwithstanding the above there are several things that cigarettes will ignite and several things that will ignite gasoline (as well as other ignitable liquids). FOCUS has read the studies and we have created our own experiments around cigarettes.
So the next time your homeowner says he was smoking and "accidently" lit the gasoline on fire, ask a few more questions.
do a little web search Propensity+of+Lit+Cigarettes+to+Ignite+Gasoline
Fact #1 A lit cigarette will not ignite a puddle of gasoline. (one of many experiments)
A little explosive entertainment courtesy of Hollyweird -
'Demolition Man' has the cigarette into gasoline.
Everything will burn up in the fire.
Fire is very destructive to most of the contents involved in the fire; however, everything does NOT burn up in a fire. Rarely does the fire destroy enough that we can not find the area of origin, the point of origin, and the cause of ignition.
FOCUS investigators have been on many scenes where we sifted through the debris and found a match, or a cigarette, even the pins on the end of the fluorescent tubes.
Gasoline will leave a detectable residue. Enough for a typical K-9 to detect even if it's not enough for the laboratory to confirm. (...and the laboratory MUST confirm it to be used in court!)
Coffee pots will melt. The metal parts will still be present and viewable through x-ray and lab inspection.
Fact #2 Vary rarely will all of the evidence burn up, including ignitable liquids.
Cars on fire always blow up!
First watch the 'Top 10 Best Movie Explosion' above in Myth #1
Cars do not blow up in a fire! Now there are a myriad of parts on vehicles which will sound like an explosion: tires, shocks, bumper shocks, drivelines, etc.
Understanding what an explosion is helps us to understand that cars don't blow up. An explosion is a sudden expansion in volume of, or release of gas under pressure. So a balloon popping can be considered an explosion. If the popped balloon was full of your breath then while the ballon material may burn the contents will not burn, if it was full of hydrogen and there is an ignition source close enough then the contents may burn (and very rapidly, think Hindenburg).
The speed at which the expansion takes place is the next factor. Deflagration vs. Detonation. Detonation is expansion faster than the speed of sound, deflagration is expansion slower than the speed of sound.
Fact #3 Very few things in most fires really "blow up". The container may rupture and the contents burn very fast (remember the speed of sound) and be devastating. Knowing the difference between deflagration and detonation can make the difference in correct origin and cause determination.
Sprinkler water damage
All the sprinklers will go off at once.
Mostly not true.
The most common sprinkler system found in buildings and residences only have one head activate at a time, multiple heads may activate depending on the size of the fire; however, they all activate independent of each other.
Each sprinkler head reacts and opens at a predetermined temperature based on where it is installed. People think that all the heads in the building will activate at once and create a flood. A typical fire is controlled with only one or two heads activating minimizing fire damage, 15 gallons per minute x two heads x 10 minutes equals 300 gallons of water. A typical fire hose will discharge 175 gallons per minute, times 10 minutes equals 1750 gallons of water plus a lot more fire damage waiting for the fire department to arrive and set up.
There is a system in which all the heads to activate. It is a special system that is installed in only a few locations for special applications; theatrical stages (not always), certain industrial processes, Hazardous Materials, etc. These are special systems designed to apply very large amounts of water very quickly.
Fact #4 Most sprinkler systems you will encounter have only one head activate at a time and at a typical flow rate of 14-15 gallons per minute.