Sleep gas

Sleep gas is a respiratory-based gas effect that has a chance to put creatures to sleep.

Effects
In order to be affected by sleep gas, a creature must respire and not currently have the wakeful effect. Robots and holograms do not respire and cannot be affected by sleep gas.

Sleep gas cannot seep through walls or other occluding objects, so it will remain contained by them instead. This often results in sleep gas having very high density if it is released in cramped areas, making it noticeably more potent. It can also take a very long time to dissipate if released in cramped areas.

Any creature that is not wakeful or otherwise immune to the effects of sleep gas that enters a sleep gas cloud must make a Toughness save to resist falling asleep. If they fail the save, they will fall asleep for a number of rounds dependent on the strength (Gas Level) of the sleep gas. Items such as the or  provide a bonus to the creature's saving roll for this Toughness save and reduce the save target by reducing the effective density of gas for purposes of the calculation.

Whenever a creature awakens from an involutary sleep effect, they will gain the wakeful status for 3-5 rounds.

The following formulas are used to determine the Toughness save and sleep duration:

In practice, gas density is highly variable due to a significant amount of randomization involved in gas behavior. Gas is constantly moving between cells, dissipating over time, merging with other gas, and being affected by random calculations in the game engine.

The density of sleep gas can get much higher than 100 with the Sleep Gas Generation mutation. With that mutation, a creature releases 800 density units of gas into the open cells around them each turn, and can continuously release gas for many turns depending on mutation level. This can result in very high density gas if the mutant releases all gas into the same area without moving, or if there are many nearby walls that contain the sleep gas into a smaller and more concentrated area.