Filter (Carbon Dioxide)

The carbon dioxide filter catches Carbon Dioxide. It fits any gas filter slot: two in the Filtration, two in the Portable Air Scrubber and three in the suit. In the filtration unit you read FilterType and Quantity through slot logic – the reserve starts at 100 and drops while filtering.

Carbon dioxide is not a poison in the game. It only becomes dangerous when it takes up so much room that the oxygen partial pressure falls below 16 kPa. Even so, you will filter it often:

• On Mars the air consists of about 95 % carbon dioxide according to the world data. If you want to use outside air, you take it out first.
• Combustion produces it: 2 mol of methane and 1 mol of oxygen give 6 mol of carbon dioxide and 3 mol of pollutant.
• It is released when many ores are smelted.

What you filter out is useful: carbon dioxide does not burn, is not toxic and makes a good cooling gas (28.2 J per mole and kelvin, more than nitrogen at 20.6). From 517 kPa and below 266 K it turns liquid – that saves room in storage, but can cause damage in gas pipes.

Lifetime: the reserve drops by 1 after every 145 ticks in which the filter actually catches carbon dioxide; ticks without that gas do not count. So 100 points last for 14,500 ticks, a good two hours of continuous use. At 0 it catches nothing any more. The medium filter lasts about five times, the heavy one about twenty times as long; like the normal one, both are made in the Hydraulic Pipe Bender, just from more valuable metals. The catalytic one lasts about eighty times as long, but is not endless. You cannot craft it; the trader Cosmic Curiosities sells it. How to separate gases is covered in Filtration: separating gases, changing filters, getting rid of waste gases.