Debating when to consider things that are actually flammable catching on fire outside of the written rules (the "burn" concept), and taking into consideration the whole "fireballs are instantaneous so you don't catch things on fire" rule of thumb I've come up with this-if an item reaches the "broken condition" ie half of its hitpoints down from fire damage then it has a chance of actually catching fire but not before. How easy it then is to put out is a matter of debate, but for those wizards shooting off fireballs indoors this is something to consider-grandma's quilt might be toast but the walls will only be singed so put down your fire suppression worries and get a blastin'!
If it is on fire than 1pt damage per minute that bypasses the hardness of the object (typically wood is what we are talking here) per square yard with thickness being taken into consideration by the initial ht pts of the object it seems, ...so a simple door that has been roasted by a healthy burning hands spell (15pts fire) will burn down in about two minutes after catching fire minus any reduction due to damage above and beyond (15pts), which it would would do if it takes any damage goes beyond 15pts (considering double hardness initially due to fire damage reduction). I think my math is right on that one...strong door at 5/20 could mean burning hands 15 pts #1 and #2 would take it down a bit in ht pts, then three would catch it on fire (now at 5/10 and without hardness so 5 minutes at 2pts a min if it is two sq yards of material)...now how this effects it being "broken" is beyond me but I'm sure there is a reasonable formula to apply for when an object is easier to break due to less ht pts...comments?
By the way, I'm also thinking that some sort of fire suppression magic should be available like the druid spell quench but on a much smaller level for all casters, not damaging elementals and the like and not effecting anything magical, maybe even a little cantrip effecting a 5'sq. . Don't tell me that arcane spell casters didn't figure out early on that a way to keep the angry pitchfork wielding villages off your back is to come in handy when the barn is burning down...a scroll of "minor quench" at first level effecting normal fires in a 10' square kept in the sleeves of your robe surely is magic 101. I'm all about druids always being way ahead of the game with controlling elements and all but there has to be a way to balance that out...
Ouch! Burn baby, burn!
This reminds me when first playing the new 3.5, I was given permission to play as a Psion Werebear.
Once the Psion got to 5th level, he began to use elemental burst with flame all the time. Then after about you know the 10th burst (two or three in a row) I began to worry maybe the Dm would decide the forest we were in would catch on fire... But he never did...