I'm currently DMing a play-by-post D&D 5e game. The module I'm using involves the party battling trolls in stables. Defeating trolls involves judicious use of fire damage. Stables are also often filled with (flammable) hay.

The party has its share of spellcasters who love to use fire to solve many of their problems in combat, and I've made it clear (without specifics) that using spells which include the words "A flammable object hit by this spell ignites if it isn’t being worn or carried" incur some risk of that fire spreading.

I've searched for posts regarding how to handle the spread of (nonmagical) fire, including the smoke it may generate, but have only found a few questions regarding specific spells, or this question regarding damage from one grid hex/square. Comments have additionally noted these two questions:

Beyond these questions:

  1. Are there any rules or guidance in the PHB, DMG, or other published modules or guides that I can reference to avoid making things up as I go along? Specifically I'm looking for how fast it might spread, and how much smoke it may generate (and what impacts that would have on the characters.)
  2. One would assume given the ease of starting a fire that it should be equally easy to extinguish magically but I've seen very few. I don't particularly want to give the players an unsolvable problem. How hard is it to put out a fire you accidentally start?
  • 4
    \$\begingroup\$ Ad 2 it's a real problem. Sometimes a child or a tourist can with one action cause hindreds of firefighters to fight fire for days, and cause irreparable damage to woods and neighborhoods. \$\endgroup\$
    – Mołot
    Jan 29 at 10:03
  • \$\begingroup\$ Possible (partial) duplicates: How fast does fire spread?, How does fire work in D&D? \$\endgroup\$
    – V2Blast
    Jan 29 at 21:13

1 Answer 1


There are no general rules on fire spreading, smoke generation, or extinguishing flames.

Although as you noted there are spells that state they light flammable objects on fire and there are spells that allow you to extinguish flames in an area (like Control Flames), there are no general rules.

This does not mean these things cannot happen. No TTRPG can truly cover every situation, they rely on varying degrees of real world 'common sense', which largely means it is left up to the DM. Throwing fireballs in a forest during a drought will likely cause some problems and spells that create water can help solve them.

Spelljammer Academy does feature a rule about inhaling smoke, but the smoke is just there and wasn't actually generated over time. Princes of the Apocalypse also seems to feature a rule regarding the inhalation of smoke but I do not own that adventure.

Smoke Inhalation. Any creature that needs to breathe must make a DC 10 Constitution saving throw whenever it starts its turn on the Cargo Deck. The saving throw is made with advantage if the creature’s nose and mouth is covered with damp cloth. If the saving throw is a failure, the creature gains 1 level of exhaustion.

As a word of advice from a DM who has previously ran head first into making elaborate homebrew rules, think carefully about implementing rules like this. They take time to properly develop so before committing I would ask myself a few questions:

  • Do you think it will actually enhance your game in any way? Is the extra challenge (on top of the already existing risk of potentially destroying important flammable objects that are hit with those spells) something you and your players would enjoy?
  • Do you want this to be a common risk or something that has the potential of happening only once or twice as a major challenge?

More realism is not for everyone, but if is it something you are after the written rules will unfortunately not be much of a guide.

  • \$\begingroup\$ Two of the players are very experienced DMs and are enjoying the restrictions of not being able to use their favorite spells, so that part of the mission is accomplished. It's a one-off, so doesn't need much more thought, I just wanted to recycle something that was already in use if available! \$\endgroup\$ Jan 29 at 16:20
  • \$\begingroup\$ I could have sworn there was a house fire in some module or other that had some ad-hoc rules for fire spreading but now I can't find it. And now I'm thinking I remember a reference to the spell quench, which would suggest it was 3.5 rather than 5e. \$\endgroup\$ Jan 29 at 17:01

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