Spontaneous Human Combustion

I have heard rumors about SHC all my life, and chalked them up to gullible people and the tendencies of rumors to grow and get more mysterious with retelling. However I just ran across a YouTube video that mentioned most cases of SHC can be traced to two concurrent things: alcohol consumption (usually chronic) and smoking cigarettes.

I wondered if chronic alcoholism could make your blood flammable?

Yahoo Answers wrote:

No, you'd have to drink a lethal amount of alcohol to make your blood flammable.

1% blood/alc ratio is enough to kill most people.

You'd need to be at 15%+ to make it flammable.

Also, a lot of the SHC victims were obese, leading to speculation their body fat made them go up like a candle.

So I began to wonder if drinking strong alcohol while smoking could start a fire.  Most spirits are about 80 proof, or 40% alcohol and not flammable -- but high alcohol beverages like Bacardi 151 or Everclear are most definitely flammable.  I suspect, given the right circumstances -- maybe a burp? -- the oxygen-to-alcohol mixture might be right (12-14%?) to ignite from a lit cigarette.

But that's just speculation.

We know farts are flammable (from the methane) but normal burps (no methane) are not. Possiblly an alcohol-fueled burp would be?

io9 had a page on SHC a few years ago. The comments included a lot of sensible stuff, for a change.

MrLebowski wrote:

Every serious fire expert will tell you that spontaneous human combustion is a myth (this includes my cousin who is one of the two main Fire Marshalls for Baltimore City). Every single case that has been studied forensically has proven that there was an external ignition source and that the person burned inside of a small, tightly sealed room where their body essentially smoldered but could not fully ignite due to limited oxygen, that's why the rest of the room doesn't burn.

Most times they are either drunk, unconscious, enfeebled or had some other situation like they actually died of natural causes and fell into an ignition source (fireplace, candle, etc.) which started them burning. In most cases the victim is usually at least somewhat overweight, which is also important. The small fire quickly eats up most of the oxygen in the room and then goes out, but the fat of their body acts just like a tallow candle, helping keep the slow smoldering going, often inside their body. The reason feet, ankles, and skull usually don't burn is because there is usually very little fat on those parts to help keep the fire smoldering.

The case above where they entered the room and there were flames coming out of the body was no doubt due to new oxygen being introduced into the room, allowing the hot smolder to re-ignite as a flame.

Yeah, slow smolder. I realized that my idea, about alcoholic burps possibly becoming explosive, even if that were possible it wouldn't explain the burning of a body down to ash.

Years ago (pre-www) I read several articles and saw a few blurbs on the news about this. The reasoning provided by Richard's quote is what I remember them coming up with. But I always liked the idea of someone burning to death from a fart backfiring.

Even if someone had an impossibly-high blood alcohol level, that wouldn't cause any fires. Alcohol, like gasoline and most other flammable liquids, will not burn. Only the vapors can ignite. That's why the chef describes liquors that must be hot enough to create vapors before they burn. And with the blood enclosed in vessels, away from oxygen, it just couldn't happen. But I still grin thinking of a fart backfiring.

You started reading before the age of one?

Oh wait. You said "www" not "WWII."

_Howard wrote:

Alcohol, like gasoline and most other flammable liquids, will not burn. Only the vapors can ignite.

Can you define "flammable liquids" for me?

Wikipedia can define it for you:

Wikipedia wrote:

Generally, a flammable liquid is a combustible liquid that can easily catch fire. However, it is not the liquid itself that burns, but the vapor cloud above the liquid that will burn if the vapor's concentration in air is between the lower flammable limit (LFL) and upper flammable limit (UFL) of the liquid.

Sublimation.

Sublimation? What about it?

I dunno. It seemed related somehow. Solid-to-gas directly, without a liquid stage? Kinda like a body decomposing by bursting into flames.

Maybe you had to be in my head for that to make sense.

I see what you are doing there. But the human body is mostly liquid, anyway. In fact, it is the liquid fats in the body that are primarily involved in SHC.