Fire Catching and Spreading rules, and explosions.

[Albions_Angel]

I wouldnt even know where to begin looking for this one. My PCs are about to engage in a fight in a flour mill. At night. They are attacking it, and the bad guys inside have lit it (dimly) with closed lanterns (the lanterns will be turned down and thus played as candles). The mill hasnt been running, so if my party walks in guns (or torches) blazing, its not going to go bang. But there is a fairly high chance something gets knocked over. Its a crowded space after all. I would like a mad scramble out if that happens.

So, how do I determine if a lamp is knocked over (I am thinking a luck roll by the player standing closest to it, if they make an attack), if a knocked over oil lamp starts a fire (I am thinking a single roll per knocked over lamp, in the round that it happens), and if the building explodes (I was thinking a luck roll every round after a fire has started).

Are their rules for this already? If not, what does the forum think?

[Nibbens]

So, how do I determine if a lamp is knocked over



I'd go with reflex checks. Every turn a PC passes through, ends or makes an attack next to a square containing a lantern (I'd place a lantern in the middle of a cross-section of 5 foot squares - so each lantern can be interacted with from 4 different squares) he makes a DC15 reflex check (or lower if you're dealing with low level PCs) Failure indicates he knocks over the lantern.

If the PCs get smart and go to extinguish them - a slightly lower reflex save to do so without knocking them over accidentally - or the rogue gets an extremely easy disable device check.

Treat the whole thing like a trap (actually an environmental hazard, but whatever), and don't forget to award XP for each trap they bypass, trip, or successfully make their way around. Traps award XP regardless.


how do I determine if
a knocked over oil lamp starts a fire

It does - end of story.


how do I determine if
the building explodes

This one's a little trickier. I'd go with a cumulative % chance per round:
# of rounds floors have been ignited X number of fires ignited. The number is low, but if there's a fight and they take a few rounds to get through, those numbers can rack up fairly quickly.

If/when the mill goes boom, have you thought of how much damage will be dealt? dealt per round? types of damage? (fire, force, bludgeon/piercing from falling timbers)

depending on level of your PCs - mixing up the damage might be a good idea if you don't want the party wizard spamming fire protection spells on everyone - or maybe having the wizard expend those spells would be a reasonable answer to that challenge - but that's up to you. lol.


Spreading Rules

You didn't actually ask this question - but it was in your title, so I figured I'd weigh in on this too. There's no exact rules in the books I don't think (if there are, I don't know of them) so here's how I run them.

The way I usually run a "spreading fire" is have the fire expand by 1 square on all sides every turn if the surface that is burning is really flammable - a wooden floor, for example.

If I deem the surface "flammable but not very" - it spreads 1 square on all sides every two turns.

If I deem the surface "extremely flammable" - a straw covered wooden floor that has been soaked in grease, for example - the fire spreads 2 squares every turn.

No these numbers aren't realistic - fire really doesn't spread that quickly unless it's very hot - but I don't really care that much. Simple numbers are better. 1 square per 1 turn is easy to remember and easy to implement.