system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Can a generic vacuum pump bring a large volume (air-tight room) to a certain pressure if it is left running long enough?

For instance, if you have a vacuum pump with a set VAC power can it bring any amount of volume to a certain air pressure if it is left on long enough, versus bringing a small volume to a very low amount of air pressure?
gpt
Yes. The residual pressure is determined by the leaks in your system. If you assume a perfectly sealed volume, then the only leakage will be back through your rotary pump.  
  
No, if you consider pumps that pump by depositing gas on a surface, like ion getter pumps, kryo pumps, or titan sublimation pumps. Those will saturate and need to be cleaned when "full". That means the volume to pump is limited, by the size of the pump. Getter and kryo pumps are cleaned by "baking", heating the whole volume, releasing the deposited gases and pumping it away with normal pumps, rotary or turbo. Sublimation pumps by sublimating a fresh layer of titan on the surrounding walls from a filament.  
  
Why use these other pumps, if you need normal pumps anyway? Because you can close off the pumps, that leak back into the system, pump to lower pressures and most importantly these pumps work without moving parts. If you are sensitive to vibrations this is what you need.