In SGU: "Intervention" and "Awakenings" as well as some other episodes, the destiny is shown to contain airlocks with pressure sensors. A bar moves up as the pressure goes up and when the it is at the top, a light that was first red becomes green. The user can now open the door. They also said that kino's have sensors that scan atmospheric makeup.
In SGU: "Air" and "Intervention" as well as other episodes, they opened a door unknowingly there was a hull breach and vacuum on the other side, which doesn't sound like the ancients did a good job on the doors inside the ship while it was in their capabilities to do so.
The ancients even knew there was going to be some dangers along the line, so they equipped the ship with weapons and shields that can correct hull breaches, but why didn't they put pressure sensors on their airtight doors, so you don't unknowingly open a door with vacuum on the other side?