How do fire investigators determine the cause of a blaze? 04-Mar-2003

Several years ago we had a kitchen fire and the Fire Marshall determined the cause to be mice chewing on a box of kitchen matches in a drawer also containing towels. Strange but true.

Just commenting on the fact that the cause of most fires can easily be determined.


Hi and welcome to the SDMB! I’m assuming you’re referring to the Staff Report How do fire investigators determine the cause of a blaze? which isn’t on the Home Page just yet.

So, some mouse somewhere chewed on a match and turned itself into a Mouse Toastie? Cool.

“Hey, what’s this taste–POOF!”

I’m sick. :smiley:

Yeah, but you are my kind of sick! “Mouse Toastie’” indeed.

Yep, the little bugger was still at the scene of the crime. First time I have ever heard of anything like that.

But then I did see a grocery stocker nearly set the store on fire when he dropped a box of the big kitchen matches from the top shelf. It burst into flame the minute it hit the floor and spread to the empty boxes he had laying around. Talk about embarrassed!

Screech (who likes sick people)

It’s also worth noting that Cecil writes the regular columns but doesn’t write the staff reports – this particular report came care of SDSTAFF Dex.

And SDSTAFF Dex is now moving this to the more appropriate forum, Comments on Staff Reports.

Welcome to the Straight Dope Message Board, screech, glad to have you with us. Just so’s you know for future, the Staff Reports are written by staff, not by Cecil, so we have a separate forum for 'em. (Get it? Forum for’em? I’m gonna be a poet when I grow up.)

Anyway, a great first post, and we look forward to many more!

Another source of info is “Firelover” by Joseph Wambaugh. It’s a true-crime book about a California arson investigator who was convicted of setting fires.

My mistake, sorry! I love all the articles, and credit should be given where it is due.

Obviously I am new and need to go back and read the rules again, and the other forums, to get the hang of how things are done. I wasn’t even aware of the message boards until yesterday. I promise to do better in the future. Thanks to all for the welcome and the tips!


OK… how was an article not on the boards referenced? Is it March 4th somewhere that I do not know about??? I am confused. :confused:

At the Straight Dope Homepage (, if you scroll down a wee bit, you’ll see a paragraph or two about “Join the Straight Dope Mailing List.”

Each Thursday night or Friday morning (more or less), the folks on our mailing list get a preview of Cecil’s column (which will appear on the website that Friday) and of the Staff Report to appear the next Tuesday. It is thus possible to comment on a Report a few days before it has been official referenced on the boards.

ohhhh… ok :slight_smile:

I just thought that fighting ignorance tended to create psychics…

Thanks :smiley:

Curse you, Dex! " :mad: "

[crossly puts crystal ball back in cupboard]


Hey CK you gave me away! I wanted to thoroughly confuse people with my answer as to how mice can start fires, as well as show off my ability to post improperly, LOL.

Truthfully, I thought I was commenting on an article that came out in the newsletter. Man, any more education for me today and my head will explode.

I thought this staff answer was a very good concise summary of fire investigation basics. (I’m an insurance fraud investigator and have had some training in arson investigation, but don’t do C&O analysis–that’s “cause & origin” to those of you not in the fire biz). The toughest fires on which to determine C&O are those where the fire is discovered late or is difficult to extinguish, leaving extensive damage and therefore not enough bits left to analyze.

“door jam” —umm, perhaps you meant “door jamb”? See Webster’s if you don’t believe me. Great SD STAFF piece!

A long time ago, I heard that the fire invedstigaters would have alot of trouble figuring out how the fire got started, if you use potatoe chips as an accelerant.

Is this true or just the UL it sounds like?

By the way, if you ever need to start a campfire and have “Real” potato chips on you (NOT the fat free kind), just one handful is all it usually takes to start even (moderatly) wet wood.

As a long-time employee of the largest and most respected C&O Engineering firms the country, I’ll just pass on the following facts gleaned from 12 years experience in this field.

A) In some fires it is easy to determine the cause and origin (C&O) simply because the fire is extinguished before much damage is caused. One the fire has grown to a significant size, this is no longer true. “Significant size” is hard to define, but once it gets to the size that a room or attic is burnt over, it is probably too late to be “easy”. I will refer to these fires as “significant” fires for lack of a better term.

B) In most significant fires, short of expending money like it was water, it is not possible to determine the C&O of a fire. When my firm investigates a fire, we commonly spend over $50,000 ( some times over $250,000) and hundreds of man hours (by Ph.D. Mechanical, Chemical and Combustion engineers), including burn test on suspected components (and sometimes entire buildings), and still frequently find the cause of the fire is undetermined or can be narrowed only to a few likely causes. Many C&O investigators claim they do the same with a couple of hours of investigation at the scene. Not likely.

C) When a fire department reports the fire was electrical or smoking related, this is normally (but not always) code for “we don’t have a clue what caused the fire.”

D) When a building burns to the ground, and someone tells you they know the cause, they are most lying, fooling themselves or started the fire themselves.

E) If n C&O investigators review a significant fire scene, you have about a 90% chance of getting n different causes.

F) Fire department C&O investigators are under a lot of pressure to provide a cause, so I should give them a break. They try hard, but they do not normally have the time, money, training or education to resolve the cause of a significant fire (Obviously there are exceptions).

In my experience in a Boy Scout troop full of pyromaniacs, this is not true. Even if you throw a potato chip into an already blazing fire, the grease will flash quickly, but the chip itself won’t do much of anything. There were a great many things which worked better (and although many of them were perfectly legitimate things to use to start a campfire, I’m not going to mention them in the present context).

Culture that was a great explanation of how things work, and you are right, the first person they look to is the guy who is supposed to tell them how this happened in the first place. If there is loss of life, I am sure the pressure is even worse. My hat is off to you.

Of course, answer D made me laugh out loud. I’ll have to remember that one when Joe Bob is on the news claiming to know what caused the fire.

And Chronos, you totally ruined my plans for the next family camping trip when I was going to start the campfire with nothing but a bag a Lays and a match and be the star, LOL!


I take exception to the generalized tone of culture’s statement, to some extent. It’s often not a question of an inability to determine the cause so much as as the expense. The insurance companies, if they have any suspicions whatsoever, are often willing to pay for a complete determination of cause if that will avoid paying a claim (for instance, because of an arsonous C&O).

The fact is that most fires are not so “significant” that the cause cannot be determined.

Hmm. Maybe you were using the wrong kind. Ruffled or flat?

Ive found that those flat, super cheap bargain chips work the best, the ones that have fat literally dripping off them. Also you should crush them up, not too much and not too little.