Walkway around the Pit

Hint: What are all of these things I'm walking through?

Nested hint: I've come to a point in the walkway that is torn up.
(sorry, cannot decode section)
Nested hint: I have the right equipment, but I can't repair the walkway.
(sorry, cannot decode section)
Hint: Many of the doorways are closed and locked.

Hint: I can no longer travel the walkway; security sees me and kills me.

Hint: I'm lost in an endless maze of ductwork.