Monsters following through zone doorways

[SHODANFreeman]

Actually if i remember correctly they cant get it because their Brains are to small to know that the doorknobs open most doors so they bang on it (Infected from black plague did that to the door from cells-messhall entrance if you are found) (Or they lack the AI)

I believe in Penumbra the doors connecting levels were often sliding doors that could be presumably operated by a button on the door. The Tuurngait that spotted you was so angry that he didn't notice it and just banged on the door. That's why they never follow you through those doors. Instead they just bang on them like they do normal wooden doors, hoping to break them down.

Well, that's mostly just the game's way of explaining why they don't follow you, I would like it very much if there were no doors that you could instantly be safe by going through, and that you had to evade them by hiding or running far enough away that they gave up looking, etc.