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Gases are an environmental hazard released into the air by various mutations, abilities, and items.

Different types of gas may occupy a single cell. For example, if your character has both Corrosive Gas Generation and Sleep Gas Generation, you can fill an area with both types of gas. However, the game does not currently have a way to clearly visually render both types of gas in the same tile at once, so it might sometimes appear like there is one type of gas in each single cell. You can confirm which types of gas are in a particular cell by using the Ctrl+Space keybind to inspect the cell.

Gases of the same type always merge together when entering a shared cell, so there will typically only ever be one gas "object" for each type of gas in a cell. However, that object may have higher or lower density, which is a measure of the total "volume" of that type of gas which is currently in the cell. Higher density gases typically have stronger effects, such as dealing more damage or requiring more difficult saves to resist their effects.

Gas Behavior

Density can be equated to the number of units of gas in a particular cell.

If the density of a particular cell's gas is higher than 10, there is a 25% chance per turn that the gas will spread.

  • When the gas spreads, it dissipates into a random number of adjacent cells between 1 and 4. Certain gases are seeping, meaning they can also travel into cells occupied by walls (and thus, effectively pass through those walls).
  • When a gas dissipates, the game moves a random amount of density from the gas's current cell into the adjacent cell(s). The amount of density moved into each adjacent cell is a random number between 1 and 30 (limited if there isn't 30 density available to move). The moved gas will merge with any other gas of the same type that is already in the target cell.

If the density of a particular cell's gas is 10 or lower, there is instead a 50% chance each turn that the gas will dissipate entirely (and be destroyed by the game).

A side effect of this behavior is that, when a non-seeping gas is released into a tight area, such as an enclosed hallway, it can take an extremely long time for the gas to fully dissipate, because it has less opportunity to escape into empty, low-density cells. For example, sleep gas released by an urchin belcher's drowsing urchins into an enclosed area with very tight corridors can linger for hundreds or even thousands of turns.

Gas Attributes

For more information about respiration-based gases, refer to the respiration page.

Gas Name Seeps Through Walls? Respiration-based?
confusion gas No Yes
corrosive gas Yes No
cryogenic mist No No
defoliant Yes No
File:Fungal spores.pngfungal spores No No
File:Fungal spores.pngfungal spores No No
File:Fungal spores.pngfungal spores No No
File:Fungal spores.pngfungal spores No No
fungicide Yes No
glitter dust No No
miasma No Yes
normality gas Yes No
osseous ash No Yes
plasma Yes No
poison gas No Yes
scalding steam No No
sleep gas No Yes
stun gas No Yes

Similar Phenomena

Fungal spores, which are expelled by the brooding azurepuff, brooding goldpuff, brooding jadepuff, and brooding rosepuff, act identically to gases (technically, they are implemented as gases in the game engine). Fungal spores are non-seeping and are not respiration-based. For more information about fungal spores, refer to the fungal infections page.