Dust explosion

[Soultpp]

This is primarily a question for 3.5, but can cross to Pathfinder, and other systems relatively easily.

Basically what I'm looking at is how much damage would such an explosion cause? I know they can be very dangerous IRL so I had thought about using something like this as a trap, especially when it is so easily and cheaply setup. Assuming that its just common dust (flour most likely) and considering that a 1kg (2.2lb) dispersion is enough to fill almost 1300 sq ft.
But translating it into actual dice numbers, as well as finding suitable DCs for crating, searching, and disabling is where I am lost. I am planning on making a rogue who makes battlefield and other minor traps as a specialty, and this would be such an easy and potent one to manage.

Anyone got any advice/suggestion on how to nail down the numbers here? And maybe even a CR for such a trap.

 

[Greenfield]

There are a lot of RL situations that don't come up in game worlds.

When was the last time your dungeon-delving team of adventurers had to deal with the consistently chill temperatures under ground? 50-60 degrees farenheit are almost universal when you get more than 10 feet deep.

When was the last time they worried about their air supply in a cave?

When was the last time the discovered that a Fireball spell consumes all the oxygen in the blast area?

If you're like most games, the answer to those and other exiting questions is "never".

And there's a good reason not to include dust explosions in the game: There will always be some enterprising would-be Alchemist who will try to engineer and argue for yet another way to make explosions, without having to expend spells.

I've mentioned before that I don't allow gunpowder or firearms in my game worlds. I've had players try to argue that their PC "researched" gunpowder, storage batteries, and/or various advanced weapons. Others have claimed to have "traveled to the future" to explain the Remington rifles, AK-47s and M-16s they want me to allow.

My answer is always the same: This isn't the real world, it's a parallel world with different laws of physics, a place where magic works but a lot of technology doesn't.

You want to mix charcoal, sulfur and bat droppings (a major source of nitrate)? Cool. When you light it it will smoulder and smoke, smelling like burning sulfur and bat droppings. It won't explode. You want it to explode? Add magic. (Sulfur and bat guano are the material components for Fireball ).

Want to run a telegraph system powered by lead/acid batteries, the way much of the network was in the American old west? Dipping lead and copper plates into acit is a great way to etch and slowly destroy lead and copper plates. No usable electricity will result.

I'd make the same ruling for methane and dust explosions.

If someone wants to know just how physics have changed, say that the near-instantaneous thermal exchange needed for an explosion can't happen without magic.

Think of every way you could abuse the rules if you include such things as gas and dust explosions. Now presume that your players are as evilly creative as you are.

Rule accordingly.

 

[Celebrim]

I ad hoc ruled a dust explosion about 3 weeks ago, after a I had a trap that involved producing choking dust clouds made of very fine dry particles, and some PC thought it would be a good idea to cast burning hands in that scenario.

IRL, how much force a dust explosion has depends on the size of the particle, the density of the particle in the atmosphere, total volume of the dust contaminated area, and the average surface area of the particles. There are way too many factors to determine exactly based on the inputs (which are generally unknown) so the best answer is probably to make it reasonable for CR 1-3 type trap. I ruled his fire spell spontaneously transformed into a 5HD fireball centered on the emanation point of the spell (himself). Fortunately, he had fire protection up and the only other PC in the blast radius was a rogue with evasion, so little harm was done.

More rigorous simulation would be to treat the explosion similar other explosives in your rules, probably with a combination of fire damage, with possible falling damage from being thrown (as if thrown or bullrushed, depending on the rules you have), and shrapnel damage if something in the area can get swept up by the explosion, and different degrees of effect depending on how far you are from the explosion. However, I didn't have anything prepared, and winging this works just fine.

Keep in mind anything you allow, your PC's will copy. Flour itself isn't particularly dangerous, and I'd tend to make explosions of typical flour on the low CR end of the scale. Where you get dust explosions from flour tends to be in mills where very fine particles of flour tend to accumulate over time. Rice flour shed from rice abrading nearby grains is particularly bad.

 

[delericho]

I would treat it, essentially, as a non-magical fireball. So, something like:

Dust Explosion Trap: CR 3; mechanical; location trigger; manual reset; spell effect (fireball, 5th-level wizard, 5d6 dire, DC 14 Reflex save half damage, cannot be dispelled); Search DC 26, Disable Device DC 26. Cost: 2,500gp, 200XP.

 

[Celebrim]

There are a lot of RL situations that don't come up in game worlds.

Depends on the game world.

When was the last time your dungeon-delving team of adventurers had to deal with the consistently chill temperatures...

When they climbed to the lip of the 16,000 high volcano. They were also suffering from altitude sickness and fatigue from a forced march.

...under ground?

Well, they haven't been in a cold cavern in months of game time, but they did have a problem of suffering from consistently hot temperatures in a cave carved by a hot spring a few sessions back. Heat fatigue from the cave and from having to camp in the thermokarst area over night (and not getting a very good sleep) were major issues, particularly for a severely wounded PC.

50-60 degrees farenheit are almost universal when you get more than 10 feet deep.

Sure, but speaking from experience, anything over about 64 degrees farenheit makes for a miserably hot caving experience, and even below that I've seen cavers prefer to cave in just their boots to keep from overheating. Caves are extremely humid and the ones real cavers go in require arduous aerobic exercise. Where hypothermia gets to be a big problem in caves is in stream passages - being immersed for hours in 50 degree water is no joke. We did have some hypothermia issues months ago game time (years ago IRL) where a PC slipped off a flowstone and landed in a pool of 54 degree water.

When was the last time they worried about their air supply in a cave?

Usually they adventure in areas that are so huge, air supply is not a major problem. One recent cavern was big enough, it had its own weather.

When was the last time the discovered that a Fireball spell consumes all the oxygen in the blast area?

Hasn't come up, but I expect it too at some point given how fond they are becoming of that spell.

And there's a good reason not to include dust explosions in the game: There will always be some enterprising would-be Alchemist who will try to engineer and argue for yet another way to make explosions, without having to expend spells.

Carrying around a kilogram of dust, and trying to disperse it evenly through a volume of a 1000 square feet, and then light it from a distance sounds like an interesting proposition. However, in my games enterprising alchemists are all the time trying to find a way to make explosions. It's expected, and desired. Carrying around explosives is its own penalty anyway.

I've mentioned before that I don't allow gunpowder or firearms in my game worlds.

I don't either, but mostly for reasons of flavor and not balance or objection to the concept. Firearms badly skew the game against the PCs anyway, so allowing them would punish the players. I do allow explosives, but as I tell my players, no known alchemical explosive is more stable than nitroglycerin. It's not that you can make nitroglycerin, it's that if you make its equivalent in the game and stabilize it like dynamite - THAT is as stable as raw nitroglycerin. Review my game described earlier in the post and you'll see why carrying around explosives isn't the smartest idea.

I've had players try to argue that their PC "researched" gunpowder, storage batteries, and/or various advanced weapons.

They're allowed to try, with the caveat that they should realize many very smart NPCs have tried these things before with varying degrees of success. The incident where the goblins armed their whole army with firearms and explosives is legendary on my world - and not for its brilliant success.

Others have claimed to have "traveled to the future" to explain the Remington rifles, AK-47s and M-16s they want me to allow.

Err... now that I won't allow. There is no "from the future" background available to purchase and no "from the future" concept would be approved for play. However, if there was, there would be no guarantee any of those things would exist, as it would be the future of Korrel and not Earth they'd be from.

Otherwise, I agree with you that the physics of the game world aren't the same as the physics of the real world. Any alchemist in my game world could tell you that lead can't be used to produce electricity, as its negatively aligned and renowned for its magic absorbing capabilities. Lead would actually moderately dampen electricity on Korrel.

Think of every way you could abuse the rules if you include such things as gas and dust explosions. Now presume that your players are as evilly creative as you are.

Rule accordingly.

My players are no where near as evilly creative as I am. They tend to act accordingly.

 

[Soultpp]

I would treat it, essentially, as a non-magical fireball. So, something like:

Dust Explosion Trap: CR 3; mechanical; location trigger; manual reset; spell effect (fireball, 5th-level wizard, 5d6 dire, DC 14 Reflex save half damage, cannot be dispelled); Search DC 26, Disable Device DC 26. Cost: 2,500gp, 200XP.

This sounds about what I was looking for, but I have to ask why the cost? I assume its just set by the trap rules. I would have to lower that if possible, and I may consider lowering the dmg but adding a secondary bull rush for the concussive force (since fireball is clearly stated as not having a shockwave)

There are a lot of RL situations that don't come up in game worlds.

When was the last time your dungeon-delving team of adventurers had to deal with the consistently chill temperatures under ground? 50-60 degrees farenheit are almost universal when you get more than 10 feet deep.

When was the last time they worried about their air supply in a cave?

When was the last time the discovered that a Fireball spell consumes all the oxygen in the blast area?

If you're like most games, the answer to those and other exiting questions is "never".

And there's a good reason not to include dust explosions in the game: There will always be some enterprising would-be Alchemist who will try to engineer and argue for yet another way to make explosions, without having to expend spells.

I've mentioned before that I don't allow gunpowder or firearms in my game worlds. I've had players try to argue that their PC "researched" gunpowder, storage batteries, and/or various advanced weapons. Others have claimed to have "traveled to the future" to explain the Remington rifles, AK-47s and M-16s they want me to allow.

My answer is always the same: This isn't the real world, it's a parallel world with different laws of physics, a place where magic works but a lot of technology doesn't.

You want to mix charcoal, sulfur and bat droppings (a major source of nitrate)? Cool. When you light it it will smoulder and smoke, smelling like burning sulfur and bat droppings. It won't explode. You want it to explode? Add magic. (Sulfur and bat guano are the material components for Fireball ).

Want to run a telegraph system powered by lead/acid batteries, the way much of the network was in the American old west? Dipping lead and copper plates into acit is a great way to etch and slowly destroy lead and copper plates. No usable electricity will result.

I'd make the same ruling for methane and dust explosions.

If someone wants to know just how physics have changed, say that the near-instantaneous thermal exchange needed for an explosion can't happen without magic.

Think of every way you could abuse the rules if you include such things as gas and dust explosions. Now presume that your players are as evilly creative as you are.

Rule accordingly.

A couple points I'd like to respond to here. First off, gas explosion is canon in at least the Forgotten Realms universe, it was used to blast apart a whole mountain top in one of the novels. That being said, the gas would be assumed to be far too rare to replicate that more than once in an age as the circumstances for it were unique, and the mind behind it was also an accomplished alchemist and had a whole clan of dwarven craftsmen as well as one special dwarven doodad to actually make it happen safely.

As for the whole 'you can't do anything without magic' thing, that seems a specious argument meant to avoid the issue to me. I understand and accept some difference in world physics but just saying 'magic only' grants all of the tinkerers and craftsmen a useless vocation. Some things maybe, and I would agree that this would be a case of 'lesser result than magic' perhaps. Also there is a distinct difference between magical and non-magical fires, with magical ones generally being much stronger than an equivalent non-magical one.

I wasn't suggesting anything like making gunpowder though. In fact, that exists in many realms already in the form of smoke powder. And I would never do something like trying to bring modern guns into a fantasy setting since that contravenes the spirit of the setting choice in the first place. (Though any gun can be insanely easily defeated by a simple heat metal spell, and likely causing explosive damage to the wielder in the process.) Beyond that, if the players want to use guns, why not just play in a modern setting?

Also things like liquid flammables exist and are utilized by the rules in a mirror of real world physics (making a vial of lamp oil into a Molotov, for example).

I also want to say that I as a player would never rely on this one trick to get out of everything. Sure it might work once, maybe even twice, but there are a lot of creatures that, even if they aren't immune to magical fires, are immune to non-magical ones and as a player, if I abused a single trick too often, or even after the first try, I would expect the DM to bring in such creatures to counter it or even use it against me as well. As a DM, that is exactly what I would do, though I might wait to see if it was a 'one off' brilliant tactical move, or if the players were becoming dependent on this 'non-magical fireball'. I would also point out that, at its basest, cheapest cost this trap would never match a wizard's fireball in efficacy because of the severe restrictions on location one would need to get a good blast and the fact that, as the components are listed without GP cost, the spell itself is essentially free as well and so insanely more cost effective than the non-magical equivalent and further upgrade-able for no additional GP cost via metamagic feats.

Also, as far as air supply in caves... Why else would they have made rules regarding suffocation?

As for fireball using up all the oxygen... It depends on the DM really, in the one example from our group in which this could have been an issue, the point was moot as the fireball killed almost all of the party when cast. (That will tend to happen when it is cast by a wizard from the back of the party in a 5x5 room/hallway.) If there had been a side effect such as a cave in just prior to the casting, then this it would have been a logical question to ask as it would have been a serious concern.

 

[Greenfield]

In no particular order: Suffocation rules are used for drowning and/or strangulation.

D&D novels aren't rules.

Tinkerers and Alchemists' work is fare from meaningless in a "no gunpowder" world. They're simply prevented from producing gunpowder and similar explosives.

I didn't say, or even suggest, that "you can't do anything without magic." I just said you can't make explosions. My suggested "law of physics" was that the sudden heat transfer needed to turn gunpowder from a flash-fizzle into a "boom" didn't work. Pouring water into an active volcano will produce clouds of steam, but not steam explosions: It just can't boil and expand that fast. (IRL a Greek island once erupted and blew itself out. When the hollowed out cone collapsed and the sea rushed in, it hit the hot lava bed and caused a steam explosion that could be hears as far away as Norway. The resultant tidal wave destroyed the Minoan fleet, turning them from a mighty sea-born empire into a small island of ruins over night.)

In 3.*, there are no rules for lamp oil Molatov's. They don't exist to the best of my knowledge. You use alchemist's Fire instead. And in any case firebombs aren't explosions, just incendiary.

 

[delericho]

This sounds about what I was looking for, but I have to ask why the cost? I assume its just set by the trap rules. I would have to lower that if possible, and I may consider lowering the dmg but adding a secondary bull rush for the concussive force (since fireball is clearly stated as not having a shockwave)

I took the price from a comparable trap in the DMG. I don't think there's any particular logic behind it. (Besides, if it's just a trap you're going to place in a dungeon your PCs are exploring, you can ignore the price.)

Adding the secondary bull rush would be fine. One of the beauties of 3e is that it can handle just about anything - it's just a question of how much effort you want to put in on the detail work.

 

[Celebrim]

In no particular order: Suffocation rules are used for drowning and/or strangulation.

Suffocation rules are fine for drowning, but terrible for death by strangulation. The mechanism of death by strangulation is not the same as the mechanism of death by suffocation.

I'm not nearly as worried as you are about the players performing stunts. If the players can arrange to collapse a volcano and pour sea water directly into the magma chamber, I see no reason a realistic explosion should not occur even if the physics of the universe are slightly different from that of the real world. If players can arrange to atomize flaming oil without igniting it, and only after it has reached a uniform density of fine droplets in a large volume, then spark the entire thing, I see no reason a thermobaric explosion should not result from this circumstances even though the physics of the imagined world are different from the real one. For one thing, these things that are being proposed are so fantastically difficult that I can't imagine players pulling them off without equally grand and fantastic skills. One doesn't produce a thermobaric explosion just by throwing some flour in the air and sticking a flame to it. If a player wants to argue with me that he ought to be able to do that, then he better be prepared to take a handful of flour and a cigarette lighter out into the yard and demonstrate the principle for me. I promise to simulate in game exactly whatever results he achieves, but if he's not prepared to do so, then he's going to have to accept my sense of how futile and difficult such a demonstration would be.

In 3.*, there are no rules for lamp oil Molatov's.

There are no rules for millions of things that players might attempt to perform. If you as a DM aren't prepared to handle those circumstances, and are giving recourse to saying things like "the books don't tell me how to handle this situation", then you are hampering your own development as a DM.

 

[Celebrim]

This sounds about what I was looking for, but I have to ask why the cost?

May I inquire as to whether you are going to be the DM of this game, or a player within it?