Maintenance

All of the tunnels outside of the main halls are probably maintenance. This is the most common access on the station, though not completely ubiquitous, and the area is marked by its proximity to every other area, its poor lighting, and its exposed pipes.

These are usually safe, and full of gear that would otherwise be completely restricted like sunglasses, gas masks and even backpacks. Some roles start out with full maintenance access by default, some can access the maint doors connected to their workplaces, and some can't access it at all. Maintenance is also where you'll find the entrances to the solars and certain external airlocks.

If you see something in the maintenance tunnels that doesn't look right (i.e. BLOOD IS EVERYWHERE), inform the Detective as he's the only security person who can do something useful with it, besides the Head of Security who really shouldn't be that far from the brig. It is possible to disappear on purpose in the tunnels, but hiding requires you to go really deep into the station's bowels to escape the eyes of roaming security and crew. The AI will often kill people in maintenance when rogue and, if need be, hide the bodies with a Cyborg.

One last note, just hope it isn't GARBAGE DAY!