Chlorine Gas

Chlorine Gas is an in-game gas element that appears naturally and can be manufactured and harvested in multiple ways. It is produced renewably by the Chlorine Gas Vent and as a byproduct of the Rust Deoxidizer; Bleach Stone in its item form emits Chlorine unless that item is pressurized (for example by water). Chlorine can also be harvested from certain rocket Space POIs: Chlorine Clouds yield 135–405 kg per cycle (gas or liquid), while Radioactive Gas Clouds yield 9.1–36.4 kg per cycle. Because Chlorine has a relatively high condensation point and very low thermal capacity and conductivity, small amounts of Liquid Chlorine may occur naturally in the Frozen Biome where temperatures can reach about −40 °C.

Mechanically, Chlorine is treated like other gases in Oxygen Not Included: mass per tile is the relevant measure rather than a separate atmospheric pressure unit. Its low specific heat and thermal conductivity make Chlorine change temperature quickly and resist transferring heat to other materials. Chlorine appears visually as a green gas and can form liquid under sufficiently cold conditions.

Chlorine has several gameplay uses and interactions. Some critters and plants require or interact with Chlorine: Squeaky Pufts consume Chlorine and excrete Bleach Stone; a single Chlorine vent can sustainably support 1–2 Squeaky Pufts. Certain plants use Chlorine directly: Dasha Saltvines require a small amount of Chlorine to grow in addition to Sand fertilization (one vent can support 11–23 plants continuously, though Chlorine must be cooled before supplying them), Balm Lilies prefer a Chlorine atmosphere (but do not consume Chlorine), and Gas Grass (available via rockets) consumes Liquid Chlorine—one vent can support 84–168 Gas Grass plants continually. Chlorine can be stored or transported in gas or liquid form depending on temperature and pressure control.

Contrary to some expectations, Chlorine does not cause direct permanent damage to Duplicants; exposure behaves similarly to other non-breathable or irritant gases (for example, it causes eye irritation and slowness rather than ongoing damage). Because it displaces breathable oxygen, sustained Chlorine atmospheres still require life-support countermeasures. Exosuits or Atmo Suits that supply oxygen are commonly used to allow Duplicants to work in Chlorine-rich areas.

Practical notes and tips:

• Use a Chlorine Gas Vent as a renewable production source; pair vents with gas filters and automation to route Chlorine where needed and keep it away from living spaces.
• When farming Dasha Saltvines, chill the Chlorine before piping it to plant tiles to avoid overheating; insulate Chlorine plumbing if needed because of its low heat capacity.
• Squeaky Puft farms convert Chlorine into Bleach Stone; collect Bleach Stone carefully because in its item form it will emit Chlorine unless submerged or pressurized.
• Liquid Chlorine is useful for Gas Grass grown via rockets; keep it cold and contained to prevent unwanted condensation into surrounding areas.
• When harvesting Chlorine from rockets, prefer Chlorine Clouds for higher yields; Radioactive Gas Clouds produce smaller amounts and introduce radiation concerns.
• Control mass per tile (gas mass) to manage atmospheric behavior and layering; remember that the game does not use a separate pressure unit but rather gas mass and tile volumes.
• Use protective suits or oxygen-supplying equipment for duplicants working in Chlorine atmospheres to avoid breathability penalties and eye irritation effects.