Consequences of setting a forest on fire...

[magnusmalkus]

Ok... quick setup..

The PC's are battling spiders in a very densely packed pine forest. Flammable spider webbing hangs all around in mighty abundance.

The PC's are evenly matched but are approaching a disadvantage due to waning resources. One of the party members has fallen twice already. Dire circumstances call for dire actions... they decide to set the webbing on fire (yet, they NEVER considered retreat /eyeroll).

What now? I think I realize it's a TOTAL DM's call... but... barring injecting TOO much 'reality' into this situation, what might be some consequences?

The forest is very dense and wild. There is no easily discernible trail. It is daytime, but the forest is dark due to a tight canopy further enshrouded due to a very high density of spider webbing among the branches (these monstrous spiders trap birds). The players have no ranger or druid in the party, the party has been relying on untrained survival checks to navigate their way to their destination.

What about the rate the fire spreads? Can the PC's outrun it in these circumstances? What kind of shelter would protect them (a deep cave, most likely... but anything else)? What about smoke? What else have I not thought of?

Help please?!

 

[Celebrim]

What about the rate the fire spreads?

Sadly, the game is very light on these rules. I've been meaning to do a write up myself.

The big things that matter in a forest fire are how dry the fuel is and how high is the wind speed.

If you are in a typical temperate forest in a typical spring, the fire is going to spread very slowly and probably will never become a true crown fire. This is a small ground fire doing 1d6 damage per round you are exposed. Whether or not giant spider webs provide unusually good fuel is something you'll have to decide. Once the fire crowns (that is, goes up into the leaves and starts burning the whole tree) or if there is a lot of dry dead wood on the ground, damage goes up to 2d6 per round of exposure plus you have a heat exposure effect.

In general, the rules imply that fuel naturally spreads among dry tinder at 5'/round in all adjacent spaces (in a cross pattern). That you can easily outrun or just out walk. But 'common sense' suggests that wind speed is going to matter. I'd suggest that wind speed spreads a fire an additional 5' in the direction of the wind per round for each 3mph of the wind. So a typical breezy 15mph wind on typical tinder means the fire spreads about 30' per round - only about half the speed of a fast walk, or about full speed through difficult terrrain.

I'd have the smoke extend out about 30' in front of the fire in the direction of the wind or 90' if the fire crowns, further if you have a lot of wind. Heat damage should extend out in front of the flames by an equivalent amount, but in general I think you get away fairly easily unless you are in an arid climate and the wind is high. The difficulty of the terrain and the possibilty of choking on smoke in the first few rounds are the main hazards in your description. Of course, you can make this as lethal as you like by adjusting the parameters.

Can the PC's outrun it in these circumstances? What kind of shelter would protect them (a deep cave, most likely... but anything else)? What about smoke? What else have I not thought of?

In general, I'd expect the PC's can outrun a typical forest fire unless you are in high summer during a draught with a high wind. Alternately, if you can get about sufficiently far from the fire - say 30 yards - you probably can weather it. Heat exhauastion might be a problem in a long fire, but if you are in water that should probably be ok. A cave should be ok provided its deep enough that it doesn't fill up with smoke.

 

[Dark Dragon]

I have just quickly checked the SRD:

Smoke Effects

A character who breathes heavy smoke must make a Fortitude save each round (DC 15, +1 per previous check) or spend that round choking and coughing. A character who chokes for 2 consecutive rounds takes 1d6 points of nonlethal damage.

Smoke obscures vision, giving concealment (20% miss chance) to characters within it.

Heat Dangers

Heat deals nonlethal damage that cannot be recovered until the character gets cooled off (reaches shade, survives until nightfall, gets doused in water, is targeted by endure elements, and so forth). Once rendered unconscious through the accumulation of nonlethal damage, the character begins to take lethal damage at the same rate.

A character in very hot conditions (above 90° F) must make a Fortitude saving throw each hour (DC 15, +1 for each previous check) or take 1d4 points of nonlethal damage. Characters wearing heavy clothing or armor of any sort take a -4 penalty on their saves. A character with the Survival skill may receive a bonus on this saving throw and may be able to apply this bonus to other characters as well. Characters reduced to unconsciousness begin taking lethal damage (1d4 points per hour).

In severe heat (above 110° F), a character must make a Fortitude save once every 10 minutes (DC 15, +1 for each previous check) or take 1d4 points of nonlethal damage. Characters wearing heavy clothing or armor of any sort take a -4 penalty on their saves. A character with the Survival skill may receive a bonus on this saving throw and may be able to apply this bonus to other characters as well. Characters reduced to unconsciousness begin taking lethal damage (1d4 points per each 10-minute period).

A character who takes any nonlethal damage from heat exposure now suffers from heatstroke and is fatigued.

These penalties end when the character recovers the nonlethal damage she took from the heat.

Extreme heat (air temperature over 140° F, fire, boiling water, lava) deals lethal damage. Breathing air in these temperatures deals 1d6 points of damage per minute (no save). In addition, a character must make a Fortitude save every 5 minutes (DC 15, +1 per previous check) or take 1d4 points of nonlethal damage. Those wearing heavy clothing or any sort of armor take a -4 penalty on their saves. In addition, those wearing metal armor or coming into contact with very hot metal are affected as if by a heat metal spell.

Boiling water deals 1d6 points of scalding damage, unless the character is fully immersed, in which case it deals 10d6 points of damage per round of exposure.
Catching On Fire

Characters exposed to burning oil, bonfires, and noninstantaneous magic fires might find their clothes, hair, or equipment on fire. Spells with an instantaneous duration don’t normally set a character on fire, since the heat and flame from these come and go in a flash.

Characters at risk of catching fire are allowed a DC 15 Reflex save to avoid this fate. If a character’s clothes or hair catch fire, he takes 1d6 points of damage immediately. In each subsequent round, the burning character must make another Reflex saving throw. Failure means he takes another 1d6 points of damage that round. Success means that the fire has gone out. (That is, once he succeeds on his saving throw, he’s no longer on fire.)

A character on fire may automatically extinguish the flames by jumping into enough water to douse himself. If no body of water is at hand, rolling on the ground or smothering the fire with cloaks or the like permits the character another save with a +4 bonus.

Those unlucky enough to have their clothes or equipment catch fire must make DC 15 Reflex saves for each item. Flammable items that fail take the same amount of damage as the character.

Maybe it helps a bit, but a lot is up to the DM. As Celebrim pointed out, wind speed is an important parameter for a spreading fire.

 

[ExploderWizard]

Lots of flammable webbing+ dense pine forest w/o trails+ fire = probable TPK and a rather large, fast spreading forest fire.

Heavy pine forests have an abundance of very dry pine needles on the ground. Once the fire ignites those fast burning dry needles, it will spread at such a speed that PCs without magical means to leave the area will be enveloped and burn up.

In other words, a much worse plan than retreating.

 

[Dark Dragon]

Me again, should have checked the SRD for FOREST FIRES first

Forest Fires (Cr 6)

Most campfire sparks ignite nothing, but if conditions are dry, winds are strong, or the forest floor is dried out and flammable, a forest fire can result. Lightning strikes often set trees afire and start forest fires in this way. Whatever the cause of the fire, travelers can get caught in the conflagration.

A forest fire can be spotted from as far away as 2d6×100 feet by a character who makes a Spot check, treating the fire as a Colossal creature (reducing the DC by 16). If all characters fail their Spot checks, the fire moves closer to them. They automatically see it when it closes to half the original distance.

Characters who are blinded or otherwise unable to make Spot checks can feel the heat of the fire (and thus automatically “spot” it) when it is 100 feet away.

The leading edge of a fire (the downwind side) can advance faster than a human can run (assume 120 feet per round for winds of moderate strength). Once a particular portion of the forest is ablaze, it remains so for 2d4×10 minutes before dying to a smoking smolder. Characters overtaken by a forest fire may find the leading edge of the fire advancing away from them faster than they can keep up, trapping them deeper and deeper in its grasp.

Within the bounds of a forest fire, a character faces three dangers: heat damage, catching on fire, and smoke inhalation.

Heat Damage

Getting caught within a forest fire is even worse than being exposed to extreme heat (see Heat Dangers). Breathing the air causes a character to take 1d6 points of damage per round (no save). In addition, a character must make a Fortitude save every 5 rounds (DC 15, +1 per previous check) or take 1d4 points of nonlethal damage. A character who holds his breath can avoid the lethal damage, but not the nonlethal damage. Those wearing heavy clothing or any sort of armor take a -4 penalty on their saving throws. In addition, those wearing metal armor or coming into contact with very hot metal are affected as if by a heat metal spell.

Catching on Fire

Characters engulfed in a forest fire are at risk of catching on fire when the leading edge of the fire overtakes them, and are then at risk once per minute thereafter.

Smoke Inhalation

Forest fires naturally produce a great deal of smoke. A character who breathes heavy smoke must make a Fortitude save each round (DC 15, +1 per previous check) or spend that round choking and coughing. A character who chokes for 2 consecutive rounds takes 1d6 points of nonlethal damage. Also, smoke obscures vision, providing concealment to characters within it.

Most of it is covered already in my earlier post. But a CR of 6 is a number that probably exceeds something that your party can handle, at least I interpret your description in that way

 

[the Jester]

The last time there was a pc-created forest fire in my campaign, there was a TPK - 1. Which is to say, one pc- a halfling rogue and NOT the pyromaniac in question- survived, after making a bunch of different saves, checks, etc and finally finding a river to hide out in.

 

[Celebrim]

Maybe it helps a bit, but a lot is up to the DM. As Celebrim pointed out, wind speed is an important parameter for a spreading fire.

The 120' feet per round you site from the SRD is also near the maximum spead that forest fires are observed to spread at, and I think represents something close crown fire or tall dry grass fire in summer with 30mph winds.

I think that's excessive personally for an average fire, but I'm still reading the forestry services pamplet on calculating fire ground speed and I probably won't have it digested (because I'm also prepping for this weeks game, which won't have forest fires) until this weekend. Even at 30' per round, that fire is going to be plenty fast if the players are trying to plow through underbrush. Characters in heavy armor are likely dead if there is any difficult terrain at all.

The SRD on forest fires captures the effects of extreme heat fairly well, but neglects the 2d6 lethal damage per round you take for being in a square that is actually on fire. The SRD also fails to note that once you get to lethal oven level heat (the air temperature is in this case above 570F), heavy clothing stops being a further problem - though metal armor still would be. It looks like a copy paste from the heat damage rules.

 

[Celebrim]

Heavy pine forests have an abundance of very dry pine needles on the ground. Once the fire ignites those fast burning dry needles, it will spread at such a speed that PCs without magical means to leave the area will be enveloped and burn up.

I've burned quite a bit of pine needles in my day. Pine needles do go up really fast, but they also only burn hot for a few rounds and produce nice safe 'black' ground in their wake. Most D&D characters can readily survive a detritus fire like that, even if most real people (low level commoners and experts) wouldn't. The big danger IMO is young dry trees that will quickly spread the fire up into their branches. If there has been rain recently, this fire is likely to go out without spreading very far. But if everything is dry, the risk is the fire won't necessarily stay on the ground - in fact, with the webs as 'ladder' its pretty much gauranteed not to. That's when it gets nasty and even high level characters are going to die without special resources.

 

[amerigoV]

The key consequence is that a werebear in hybrid form comes out and kicks your ass for setting the forest on fire.

 

[magnusmalkus]

Celebrim: Thanks for your help but PLEASE do not waste your time working out game mechanic specifics for MY benefit.

And yes, CR 6 is a bit much for the party of 5 level 3 PC's.

There are other factors that could mitigate the fire. THe players pointed out that the smoke would easily alert the local good-aligned forest dwellers and the druidic circle that is known to keep an eye on these (spider infested) woods. Surely they could bring weather-spells to bear to help contain the fire. Wouldn't forest dwellers (elves gnomes) protect their portions of the woods from fire, wouldn't they have some kind of plan? I'm sure they would.

I think the bigger issue I'm grappling with is players who take actions who's consequences are beyond the scope of the adventure.

/shrug