I'm lost in an endless maze of ductwork.

Hint 1 of 7:

You mean you didn't leave a trail of bread crumbs?

Hint 2 of 7:

It might help to draw a map from the point where you entered the vent.

Hint 3 of 7:

Do you recall that when you entered the vent, you dropped down into the
ductwork?

Hint 4 of 7:

The exit is overhead.

Hint 5 of 7:

As you navigate through the ductwork, you'll eventually come to one very dark
dead end.  This is where you entered the vent originally.

Hint 6 of 7:

Turn around 180 degrees so that you're facing back into the duct tunnel.

Hint 7 of 7:

Now look up.