Gases Not Being Sucked Into Space Vacuum

The picture doesn't show at what pressure the gas is. Space-vacuum tiles suck all other gasses but tiles with background wall will usually have low pressure gas if you let a door/gap open (low pressure= less than 50g) for some time until it is a complete vacuum. The mod only shows there is oxygen (I think..?) but not the pressure (I just assumed from color density it would be low but I'm not sure)

I observed over a dozen or more cycles where it kept getting lower and lower, from gram, to milligrams, to micrograms, which doesn't seem very realistic, but there is so much I don't know. The creators know way more than I do about all the concepts this game requires one to learn.

Vacuums in ONI don't really suck (ie, apply a negative pressure) they just act as tiles that a gas can spread into unhindered (ie, in a 2 tile enclosed space, with vacuum in one tile, and a gas in the other, the gas will 'spread' into the vacuum tile until the pressure is roughly equal). So what's happening is that the tiles bordering the vacuum are dividing themselves into the space tiles, the space tile destroys the gas and returns to a vacuum, and the cycle keeps repeating. So it can take quite some time before the game gets down to single-digits of mcg of gas remaining and a vacuum spreads across them.