I know Cecil has addressed this, but I can’t find it on the search engine. Does anyone know where it is?
Yea, Uncie Cecil did do that subject. but you are going to browse… err, buy the book to find the answer.
It’s the “More of the Straight Dope”
spontaneous human combustion,
update on, 297-99
youll find the answer there
or you can cheek the site jazzmine
posted.
sheshh,
blowing a kiss to realm505 
In case you want more info, here is a link to the entry on SHC in The Skeptic’s Dictionary:
http://www.skepdic.com/shc.html
And, if you’re still interested, I highly recommend Secrets of the Supernatural by Joe Nickell. This excellent and interesting book includes a detailed chapter on SHC. IIRC (I lent my copy of the book to a credulous relative and she hasn’t given it back yet), Nickell includes a list of important cases of so-called SHC and debunks them pretty thouroughly. Grisly but fascinating. A&E channel also had a pretty good SHC special a few months ago. A couple of Brit firefighters had performed some experiments on a pig to prove the “wick effect.” Ick. Anyway, keep an eye on your cable listings, maybe A&E’ll repeat it soon.
Jess
Full of 'satiable curtiosity
And everyone should read Bleak House by Charles Dickens. Just because it is a good book, not because SHC is an integral part of the plot.
“non sunt multiplicanda entia praeter necessitatem”
– William of Ockham
I thought it was excellent. As the slow burn continued for hours, even the bones were reduced to ashes, just like supposed SHC.
But it was on the Discovery Channel. The narrator was Jonathan Pryce. Try Thursday nights.
I still say there’s a serial killer loose with a blow-torch.
My bad, Zig – I get A&E and Discovey confused all the time. Sorry! 
Jess
Full of 'satiable curtiosity