A CO2 scrubber, also referred to as an air filter, is a device which cleans carbon dioxide (CO2) from the air to produce clean oxygen. They are often used on spaceships and are found throughout the Ancient ship, Destiny, recognizable by the unique panel they sit behind. The scrubbers use a lime-like substance to clean the air and leave an alkaline residue behind. The scrubber canister, which holds the lime, can be removed from its holder to be "refilled" and then placed back into the device.
When the Tau'ri first arrived aboard the Destiny after the Battle of Icarus Base they discovered that many of ship's CO2 scrubbers were either malfunctioning or failing. The scrubber nodes are found behind specific grates in the wall aboard the Destiny. After investigating a malfunctioning scrubber, it was discovered that the reason it was not working was that the filter was full of alkaline, the used-up residue of whatever substance the Ancients used to clean the air. Detecting the new arrivals' problem, the Destiny's computer found a planet with a possible solution and dropped out of FTL. In a system with four possible Stargates to dial, Destiny locked out three and chose a desert planet, which could possibly have the mineral they needed. After traveling to the planet, the expedition eventually returned with a material which enabled the scrubber to function normally again. (SGU: "Air, Part 2", "Air, Part 3")
The materials recovered and used by the expedition proved effective for the better part of a year before the overall efficiency dropped to 20%. The decrease in efficiency lead to headaches for some residing on Deck Four of Destiny. It was at that time that the expedition encountered the People of Novus who helped them supplement the supplies of Lime. However the extra materials were rendered moot due to the extra personnel the expedition helped transport from the Novus colony back to Novus. There, Dr. Nicholas Rush found a material in the Novus fallout bunker that was able to keep the air clean for years when inserted into just one CO2 scrubber and replaced the lime with it. (SGU: "Common Descent", "Epilogue")
- It has been established that the Ancients launched the ship unmanned. Because of the fact that the scrubbers are depleted, it has been speculated that the members of the Destiny expedition are not the first people to board the ship.