How do astronauts prevent the buildup of carbon dioxide inside the spacecraft?



How do astronauts prevent the buildup of carbon dioxide inside the spacecraft?

In: Chemistry

There are CO2 scrubbers that remove it. This is typically either lithium hydroxide or a zeolite that will chemically bind to the CO2 and pull it out of the air. By circulating the air of the craft through this system the CO2 concentration can be kept low and the astronauts able to breath.

CO2 Scrubbing is the process of removing CO2 from the air. Originally, I believe this was done using calcium oxide filters, which react with CO2 to form calcium carbonate. This consumes the calcium oxide, which is less than ideal. Modern systems use a similar system, but not with calcium oxide. Essentially, a material absorbs the CO2, and then is treated to remove the CO2 once the material has been moved to a sealed container, before it is pumped back out to absorb more. I’m uncertain how modern systems are treated to remove the CO2 from the absorber, but as an example, when calcium carbonate is heated up a lot it releases its CO2 and returns to being calcium oxide.

Spacecraft have CO2 scrubbers. Traditionally, scrubbers use box or cylinder containing soda lime that, when air is passed through it, chemically bonds with the carbon, and removes it from the air. Once the air has passed through the scrubber, the CO2 is broken down into carbon and oxygen through a simple chemical reaction. The carbon bonds to the soda lime, and stays in the scrubber, but the oxygen passes through it.

Carbon dioxide scrubbers are use to remove the gas.
Apollo for example used lithium hydroxide (LiOH) canister and a pump to blow the air trough it and it will react with the carbon dioxide.

ISS have more complex system that can operate continuously and extract carbon diode as a gas that is dumped overboard. It is uses electricity and reversible chemical processes to extract the carbon dioxide heating up the filter in low pressure to extract the gas without need to continuously replace the filters.

When you get to 12,000 ppm the effects of CO2 start to be noticed according to nasa.This is 1.2% CO2.The Occupational Safety and Health Administration (OSHA) sets the following permissible exposure limits (PEL) (OSHA 1990): •Final Rule Limit: 10,000 ppm (1% or 7.5 mm Hg) Time Weighted Average (TWA) over a work shift up to 8 hours per day, 40 hours per week. •Transitional Limit: 5,000 ppm (0.5% or 3.8 mm Hg)
The earth is at .040%
Most spacecraft rely solely on removing the carbon dioxide with canisters that contain powdered lithium hydroxide. When air containing carbon dioxide (CO2) gets passed through the canister, it combines with the lithium hydroxide (LiOH) to form lithium carbonate (Li2CO3) and water (H2O).

Also, astronauts sleeping and therefore barely in motion, get the problem that co2 is forming a cloud around them.
To avoid this and probable problems coming with it, they have little fans blowing.