Blown out the airlock

[Savage Wombat]

Does anyone have any suggestions for handling explosive decompression in D&D?

Maybe something from Star Wars or some other d20?

 

[Crothian]

Massive amounts of fort saves to put off dieing to the next round?

 

[Jeremy]

Assuming the characters or creatures are still in an area with atmosphere and have not already been blown out into space, I'd use the hurricane strength winds rules in the DMG modified by strength checks and location (i.e. all kinds of ladder rungs bolted into place to hold on gives a bonus, nothing but smooth polished floors gives a severe penalty) to prevent actually being blown out.

As for how long a person can hold on, first give have them hold their breath as per the normal rules. Then halve the time they can hold it to account for the strain of holding on plus the effects of the change in pressure. Remember not to make the strength checks impossible (even the strongest characters rarely have more than a +6 or +7 to their strength checks) and start giving climb checks to allow characters or creatures to drag themselves to safety or towards whatever will shut the hatch.

That's my best guess.

 

[Jack Haggerty]

Use Jeremy's wind rules from the DMG to see if the characters get sucked out.

From the SRD:

Hurricane-Force Wind: All flames are extinguished. Ranged attacks are impossible (except with siege weapons, which have a –8 penalty to attack). Listen checks are impossible: All characters can hear is the roaring of the wind. Hurricane-force winds often fell trees.

Tornado: All flames are extinguished. All ranged attacks are impossible (even with siege weapons), as are Listen checks. Instead of being blown away (see Table: Wind Effects), characters in close proximity to a tornado who fail their Fortitude saves are sucked toward the tornado. Those who come in contact with the actual funnel cloud are picked up and whirled around for 1d10 rounds, taking 6d6 points of damage per round, before being violently expelled (falling damage may apply). While a tornado’s rotational speed can be as great as 300 mph, the funnel itself moves forward at an average of 30 mph. A tornado uproots trees, destroys buildings, and causes other similar forms of major destruction.

Fort Save DCs for getting "blown away" are DC 20 for Hurricane-force and DC 30 for Tornados. Personally, I'd use the effects of a Tornado.

Then, use the asphyxiation (drowning) rules to see how long they can go without air...

From the SRD:

Any character can hold her breath for a number of rounds equal to twice her Constitution score. After this period of time, the character must make a Constitution check (DC 10) every round in order to continue holding her breath. Each round, the DC increases by 1.

When the character finally fails her Constitution check, she begins to drown. In the first round, she falls unconscious (0 hp). In the following round, she drops to –1 hit points and is dying. In the third round, she dies. It is possible to drown in substances other than water, such as sand, quicksand, fine dust, and silos full of grain.

And the "cold exposure" rules to see how long it takes before they freeze to death...

From the SRD:

Cold and exposure deal subdual damage to the victim. This subdual damage cannot be recovered until the character gets out of the cold and warms up again. Once a character is rendered unconscious through the accumulation of subdual damage, the cold and exposure begins to deal normal damage at the same rate.

An unprotected character in cold weather (below 40° F) must make a Fortitude saving throw each hour (DC 15, + 1 per previous check) or sustain 1d6 points of subdual damage. A character who has the Wilderness Lore skill may receive a bonus to this saving throw and may be able to apply this bonus to other characters as well.

In conditions of extreme cold or exposure (below 0° F), an unprotected character must make a Fortitude save once every 10 minutes (DC 15, +1 per previous check), taking 1d6 points of subdual damage on each failed save. A character who has the Wilderness Lore skill may receive a bonus to this saving throw and may be able to apply this bonus to other characters as well. Characters wearing winter clothing only need check once per hour for cold and exposure damage.

A character who sustains any subdual damage from cold or exposure suffers from frostbite or hypothermia and is fatigued. These penalties end when the character recovers the subdual damage she took from the cold and exposure.

Only, make the Fort Save every round, instead of every 10 minutes, and double the DC and subdual damage... It's very cold in space.

I'll double check the Star Wars rulebook to see what it says...

 

[maddman75]

No no no. Movies have given people an unrealistic view of explosive decompression

- You aren't going to hold your breath
- You aren't going to hold onto anything
- You will die. Instantly. No save, no damage, just a decompressed husk.

First, due to the lack of pressure, all the blood in your veins will boil. The air will be forcibly ripped out of your lungs, and the soft tissues will crystallize. If it happens fast enough, there might be nothing left of the charcter but a fine pink mist.

Grisly, but you stumbled onto one of my pet peeves

 

[AuraSeer]

Argh, not that debate! People have been arguing the effects of explosive decompression since the invention of space travel. One side says it would mean instant death; the other says that you could survive for up to a minute or so. Personally I think the latter is correct, but barring an actual occurrence, it's hard to be 100% certain either way.

For game purposes, "hold your breath and climb" is definitely the way to run it, because it gives characters a chance. Instant death, no save allowed, is boring and may get the DM lynched.

 

[Krusk]

Actually, there once were NASA tests done in vacuum chambers...

I forget whether the test was purposefully testing the effects of decompression, or it was an accident while testing a space suit, but a astronaut was exposed to (near) vacuum for several seconds.

He survived easily, but relates the sensation of having moisture boil off of his eyes and tongue, because the pressure is so low.

And remember rapid and explosive decompression are two different things. Rapid decompression happens slowly enough that you can rid your lungs of oxygen, and avoid rupturing them. Explosive decompression happens faster than you can exhale, possibly causing your lungs to burst.

Here's a few web write-ups on the subject...

http://www.sff.net/people/geoffrey.landis/vacuum.html
http://www.avweb.com/articles/highalt/#decompression
http://www.straightdope.com/classics/a3_147.html

 

[Ridley's Cohort]

The only significant immediate effects would be from having the air sucked out of your lungs if you did not know to hold your breathe before the room goes to vacuum. Use some kind of drowning or axphysiation rules for that, and toss on some negative modifiers.

There would other unpleasant physiological effects, but they would be completely negligible on the time scale of minutes before you die from lack of oxygen, even if uncomfortable.

The hurricane winds are nonsense except if you have a local hull breach in a very large ship. Rooms of even fairly large size would empty of air almost instantly. The volume of air is not sufficient to cause noticeable winds except right near the breach.

 

[Jack Haggerty]

The only significant immediate effects would be from having the air sucked out of your lungs if you did not know to hold your breathe before the room goes to vacuum. Use some kind of drowning or axphysiation rules for that, and toss on some negative modifiers.

This is very, very wrong.

The immediate danger from explosive decompression is actually from trying to hold your breath.

During decompression, gasses expand (including those in your lungs and in your blood). That is how deep sea divers get the "bends"... Nitrogen in their blood stream expands, and creates bubbles in the arteries and veins. It is very painful, and if the bubbles get too large, can block blood flow, resulting in possible death.

So, say you are on a space ship, and the airlock suddenly blows... If you hold in your breath, the air in your lungs expands and will very likely burst your lungs like an over-inflated balloon. If you blow the air out, you have about 10 seconds or so before you are knocked out by hypoxia from the cold. After that, you just freeze to death and suffocate after several minutes.

 

[chilibean]

The comparison with the bends is reasonable with a couple exceptions.

Normal air pressure is somewhere around 15 psia. How deep underwater do you have to go to get to 30 psia? I don't know off hand, but it isn't very far since water is very dense. So dive to the depth of 30 psia and spend enough time there to completely acclimatize, then suddenly surface. Physiologically it should be similiar with respect to the disolved gasses in your blood boiling (assuming that gas soluability in a liquid is reasonably linear with respect to pressure in that pressure range). Is that deep enough for the bends to affect someone?

Another effect would be the fact that a full vacuum makes the boiling point of water much lower (I don't know how much, look for a PV diagram for water in a chemistry book to find out). Water ice that is above the boiling point would sublimate to a gas, just like dry ice does at room temp and pressure.

How much pressure can human lungs hold? You might be able to painfully hold 30 psia in your lungs for a short while. Maybe. Anyone ever seen those rather bizarre 'power of christ' people that blow up water bottles on TV while telling you to donate money to them? I wonder what the psi of the air is in those water bottles? I bet a hell of a lot more than 30 psia.

FYI, for anyone interested in this crap and are bored enough to still be reading this post, remember that most air pressure gauges read psig not psia. The g and a stand for guage and absolute. Absolute means psi as referenced from a full vacuum. Guage means as referenced from the current air pressure around the instrument. So a tire that normally reads 15 psi, would read ~30 psia, since your average guage reads in psig. Assuming that I am remembering correctly that typical air pressure is about 15 psia.