Pressure

Pressure

Adventurers are most likely to encounter extreme pressure in superdense atmospheres (see Atmospheric Pressure) or deep underwater (where pressure increases by about 1 atmosphere per 33' of depth).

Pressures in excess of your native pressure – 1 atm., for a human – are not always immediately lethal, but present serious risks.

Over 2 × native pressure: You risk "the bends" (see below) if you experience over 2 × native pressure and then return to normal pressure. With Pressure Support 1, the bends are only a risk when returning from over 10 × native pressure. With Pressure Support 2 or 3, you are immune to the bends.

Over 10 × native pressure: You may be crushed! On initial exposure and every minute thereafter, roll vs. HT at a basic +3, but -1 per 10 × native pressure. If you fail, you suffer HP of injury equal to your margin of failure. If your Size Modifier is +2 or more, multiply injury by SM. With Pressure Support 2, read this as "Over 100 × native pressure" and "-1 per 100 × native pressure." With Pressure Support 3, you are immune to pressure.

The Bends

When you are breathing air that has been compressed (e.g., using scuba gear), your blood and tissues absorb some of the nitrogen gas in the compressed air. When you return to normal pressure, or "decompress," this nitrogen escapes, forming small bubbles in the blood and muscles. This can result in joint pains, dizzy spells, possibly even death. These symptoms are known as "the bends." You risk the bends if you return to normal pressure after experiencing pressure greater than twice your native pressure (or 10 times native pressure, with Pressure Support 1). To avoid this, you must decompress slowly, spending time at intermediate pressures to allow the nitrogen to escape harmlessly.

Divers and mountaineers use precise tables to determine decompression times based on time spent at a given pressure. For game purposes, at up to 2 atm. (about 33' underwater), a human can operate for any amount of time and return without risk. At up to 2.5 atm. (50' depth), a human can safely operate for up to 80 minutes and return without requiring slow decompression. Greater pressures reduce the safe time without slow decompression: at 4 atm. (100' depth), it's about 22 minutes; at 5.5+ atm. (150' depth), there is no safe period.

Safe decompression involves slowly lowering the pressure, either naturally (e.g., a diver deliberately taking hours to reach the surface) or in a decompression chamber. The time required increases with both pressure and exposure time. It can be several hours – or even days.

If you fail to decompress slowly enough, make a HT roll. Critical success means no ill effects. Success means severe joint pain, causing agony (see Incapacitating Conditions); roll vs. HT hourly to recover. Failure means unconsciousness or painful paralysis; roll vs. HT hourly to regain consciousness, with each failure causing 1d of injury. Once conscious, you suffer joint pain, as described above. Critical failure results in painful death. Recompression to the highest pressure experienced lets you roll at HT+4 every five minutes to recover from all effects short of death.

An instant pressure reduction can also result in explosive decompression; see Vacuum for details. All effects are cumulative!