Re: Why does a cigarette burn in a slow controlled way?

Almost any reasonably dried, shredded lightly compacted cellulostic will 
sustainedly smolder - tobacco, hay, corn silk, marijuana, incense/punk, cow 
dung, cotton upholstery, wadded paper towel.  Sphagnum swamps during 
droughts are incredibly hazardous.  The trick is to keep the cigarrette 
smoldering without it going up in flames or going out.

Surface to volume ratio is important here.  A thin cylinder rapidly loses 
heat and so never exponentiates into full flame.  Potassium nitrate is 
often added to cigarettes to keep them lit.  There are at least 599 
additives FDA-approved for addition to tobacco products.  The text file is 
93K long, 20K ZIPped, http://www.mazepath.com/uncleal/tobacco.zip

Stored hay - big round piles! - has a nasty habit of sponteously 
combusting.  Minerals in the burning hay get hot enough to melt into glass 
(clinker), which serves as a diagnostic for what burned, how hot, and puts 
loose limits on arson ("insurance fires").

Uncle Al!