Vacuum tubes, in particular cathode ray tubes (TV tubes) have a device called a "getter". It's called that because it is supposed to "get" any gas that leaks through the glass (yes glass leaks slowly). There was a time when a TV set placed in storage for a year, and not turned on so the getter could do its job, would suffer immediate failure when it was turned on. I have not heard of this problem lately (maybe TV sets never get turned off). Perhaps we have better glass or some other improved technology.
Anyway, tube designers went to a lot of trouble to keep gas out of their tubes. It can't be good.
Anyway, tube designers went to a lot of trouble to keep gas out of their tubes. It can't be good.