What would be reasonable effects for a heavy atmosphere?

[Count Arioch the 28th]

I'm asking this question on WotC, and I don't like the answers I'm getting.

Alright, let's say I throw the PCs on a world where the atmospheric pressure at sea level is about 2-3 atmospheres. Let's also assume that the oxygen and nitrogen levels aren't really high enough to be toxic, but noticably higher than on an earth-like world.

Would would be some reasonable game effects?

[Prak]

Probably difficulty breathing, I imagine the air would be much denser, so it'd feel like breathing milk, or such. Also anything filled with "our" air would float. It'd likely cause some discomfort on the chest, but not really enough to cause harm...

....I just realized that fire spells would also be enlarged, and likely maximized, as you've just increased the levels of occurence of two very flamable elements...

[Count Arioch the 28th]

Nitrogen isn't flammable.

I'm not willing to enlarge or maximize fire spells. However, perhaps a +1 damage per die might be reasonable.

Or not. You can throw around fireballs in a vacuum, and the fact that fire can't even exist in a vacuum doesn't affect that.

Perhaps an increase in damage from natural, non-magical fires might be reasonable.

[Prak]

oops... that's right, it's just highly unstable, forgot... sorry, to be honest, I got an f in chemistry...

and the +1 per damage die should work just fine, if you want to say that the higher oxygen affects magical fire at all.

The non-magical flames thing is good, but keep in mind that some fire spells create non-magical fire. Can't think of any examples, but I think they're out there.

[virgil]

You wouldn't feel like you're breathing milk or anything that extreme. Your ears would probably feel full, as if you were in a plane gaining altitude. You'd get some blurry vision initially as your eyes react to the change.

Sound would carry better, fires would start more readily, but if it's only going to be 2 to 3 atmospheres; I don't think there's enough for anything mechanically significant to happen.

However, I'm not a medicine expert, so I don't know about the long-term effects; and when you're dealing with adventurers it's assumed they're healthy enough to not have severe medical problems for the first half hour if instantly found themselves in such an environment (maybe some low grade, Con damage poison, mechanically if you feel evil).

[Prak]

neh, so I exaggerated with the milk thing, though it would feel rather odd to breath.

I think the worst mechanical effect should be a -1 distraction penalty to concentration checks, at very worst. Specifically, horrible, railroading, senile Gary Gygax worst.

so yeah... fires start more readily, possible do extra damage, and the characters feel weird. that's probably about it.

[shirak]

Frankly, I'd just give them a -3 or -4 penalty on rolls and lift it at a rate of 1 per week of adjustment. Heavier atmosphere isn't terribly important in a game of heroic fantasy.

[Username17]

Here's a pretty decent discussion of pressure.

Basically if you are running around on a planet with 3 atmospheres outside, you'll also be breathing air that is at 3 atmospheres and it cancels out. A wall with more sumo wrestlers pushing on it from both sides is not toppled in either direction.

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So what you're actually looking at is the amount of Oxygen saturation you'll be getting. The extra nitrogen contained in an atmosphere that is the same nearly 80% nitrogen but three times as compact is essentially menaingless. You won't get the Diving Sickness because you won't experience a rapid change in pressure. The nitrogen won't come out of solution and you won't embolize.

What you will do is have more oxygen. It would be like breathing supplemental oxygen. You'd have more endurance and be generally more athletic. But long term exposure would eventually be poisonous because the higher oxygen levels would cause more oxydative damage to tissues.

Also, the flash point of most materials would be lower. Fires would also burn faster and hotter.

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Game mechanically? People get a +4 bonus to holding their breath or endurance checks and can go twice as long before they have to make those checks. People have their hit points increased by 10%. Fire and Sonic attacks are empowered for free.

Long term health effects would accumulate in the manner of your choosing, and people who entered or left such an area quickly (as by teleportation) would have to make fort saves against hilarity.

-Username17

[ckafrica]

Got to remember that some people might begin to suffer nitrogen narcosis. It would be uncommon at only 3 atmospheres but it does happen. And not a problem at 3 atmospheres but later atmospheres the concentration of oxygen does become toxic though I don't at what depth. It depends on the ratio of oxygen and or nitrogen to other gases for both effects. Higher nitrogen or oxygen environments than experienced in earths atmosphere could change everything

[Desdan_Mervolam]

Nitrogen Narcosis is caused by pressure change. It's not a funcion of concentration of air at certain pressures. If you go scuba diving and stay at the bottom for a few hours, you're not going to get the bends, not unless you're reckless about surfacing.

Really, Frank already said as much, and if nothing else his medical background means you should pay attention. And hell, Frank's like, the fifth or sixth place I've heard it from, and I've never even taken scuba classes.

-Desdan

[ckafrica]

Well I'm a dive master and nitrogen narcosis is due to the concentration of nitrogen particles due to the increase pressure which is measured by the number of atmospheres that are be pressed against you by the water. It usually begins to be noticed around 4 atmospheres (30m) but some show signs in 3 atmospheres (20m). If you are experiencing increased pressure of the same atmospheres it should affect you in the same way as if you were underwater. Same problem with oxygen toxicity but that usually happens at greater depths or at higher percentage of oxygen such as using varied air mixtures when diving. When you increase both pressure and oxygen content in the air, you can into trouble really quick. Both of them will effect you if your body is not naturally designed to handle the gas at increased quantities and pressures

[Username17]

Nitrogen Narcosis is indeed a different animal than the Bends. Rapture of the Deep happens because high concentrations of inert gas act as inert inhibitors of your neurons, creating an anesthetic activity. I didn't mention it because the warning signs are supposed to show up at 4 atmospheres, with most life threatening effects showing up at more like 10 atmospheres.

But yeah, it turns out that a small number of people get Nitrogen Narcosis at 3 atmospheres of pressure. Personally, I wouldn't worry about it. Like random meteor impacts it is a real danger, but a real small danger.

-Username17

[SunTzuWarmaster]

Make them fatigued for the first 60 minutes until they adapt to the change. The is the experience that I got for driving ~6 hours with the A/C on recirculate to the coast and then opening the windows to ask for directions. The air feels unbreathable for around an hour and strenuous physical activity is difficult. After that you adapt and everything feels cool again (give them the bonuses above for holding their breath and whatnot).

[JonSetanta]

Your life span would be, like, cut in half or more due to tumors from your cells wearing out from oxydation.

[technomancer]

Why would you feel fatigued for the first hour? You're getting more oxygen than normal. There's a reason why hard-core athletes train at higher altitude than they plan on competing at. You get used to breathing thin stuff, and when you get thicker air, you get more oxygen, which energizes you. (well, it lets you use more energy faster and possibly more efficiently, which feels like the same thing)

If anything, you should feel fatigued if you ever go back to a normal 1 atmosphere, not when you jump into the thick stuff.

[Koumei]

Fort save (DC 10? I don't know, it's a small risk as pointed out above) against Rapture of the Deep would be good for a chuckle. Specifically, if someone failed it, they all get a laugh and then move on.

Would drinking "excessive" amounts of tea combat the effects of staying there too long? What with the way antioxidants stop the oxygen molecules from randomly deciding to bond with hydrogen and create bleach inside you, or just send electrons bouncing around to damage things, if you have more than you need for regular Earth, would this essentially keep you safe?

[JonSetanta]

No one considered the energy output and requirements of mitochondria...

[Username17]

The anti-oxidant capabilities of green tea are actually pretty poor. The green tea studies keep happening because the tea council is desperate to get people to drink tea. With a percentage of people in China and India switching to coffee and soda, world tea is losing a million drinkers every year. Seriously, a million people who drank tea every day last year are not doing it this year. The tea producers are willing to do pretty mch anything to get someone somewhere to drink their tea.

If you want antioxidant activity, eat a carrot. Bu in any case, oxidative damage will still happen. Time is the fire in which we burn, higher oxygen levels make things burn faster. Oxygen is the deadliest substance we can't live without.

-Username17

[Koumei]

Ah, I didn't realise it was an exaggeration by the mystic council of tea. Still, I'll be sticking with my tea. China and India can drink whatever weird shit they like, but I will still have a drink that tastes good and relaxes me.