If you’re still stuck on this, here’s some tips.

Tip 1: Look Up.
Tip 2: The vents you can easily see aren’t relevant.
Tip 3: Say, those crates are stacked rather interestingly.

Solution
Over by the locked doorway are a bunch of crates stacked up like a staircase. Climb them, and make your way over to the end of the “platform” formed by them.

Go collect the items up there if you wish (it counts as a secret), then take a running jump off the crates, before double jumping to reach the platform that’s just hanging out with a closed white door on its left and a wall on its right.

Punt the door away by the method of your choice, break open the freshly revealed vent and go inside. Follow it, and drop down, breaking the vent grate you land on.

Hey presto, you’re now on the path forward to completing the level again! Watch out for the exploding lads.