Sometimes the answer lies below the surface of the water.
You need to swim around under water, find as many of the large red pontoon/drum/buoy things as you can (there’s one right under the “10” on your HUD for reference) and put them in the square metal cage underwater against the flat wall. This will cause the bridge to raise and you will be able to get to the far catwalk.
Don’t ask me why, it made (and still makes) just as sense to me.
(Also, any future issues in this area should go under the Apprehension thread, not Blast Pit.)
EDIT: Ninja’d.
Thank you and sorry I’m new on the forum
Hi,
I can’t seem to get into any of the openings in the fan shaft.
All the holes are either too high or too low.
I can go forwards and back left and right but not up or down.
Really stuck. Please help if possible 
Doesn’t anyone know the answer to this one?
I can’t be the only one that got to this point?
What chapter is this in?
@LukeB50
First, give people a chance to respond.
Second, there is one vent that you can access. See here for which one. You may have to crouch to get in.
@Nonimportantuser
It’s in “Blast Pit”. I have merged the threads.
Ok, sorry butI have tried all the vents.
The problem is that I can’t move up or down. The fan has me bobbing around out of reach of all vents.
The top vent is too high by a small amount and all the others are too low.
The vent you show is just a bit too low and I bob around near the red lamp but cannot go into the vent.
I have tried for several hours and pressing every key to see if any help to get me into the vent, but I just bounce off the wall.
REALLY frustrating.
Someone said that being close to the wall allows you to move down but not in my version (Steam on PC). Also that only one vent is attainable.
If you’re certain there are no vents you can get into and you’ve tried everything, there’s only one issue I can think of that might cause it.
Open the console, and make sure sv_gravity is set to 600. If it isn’t, set it to 600 by typing:
sv_gravity 600
It’s possible your gravity might have been accidentally set to 800. This is because our SP game uses 600 gravity but MP uses 800. It was a weird bug we had right back when we first implemented MP, which broke this section of SP very specifically, because you couldn’t access any vent.
That’s really all I can think of. See if that helps.
Ok. That worked. Thanks.
sv_gravity was set to 800.
Just a small point.
It would be great when people respond to requests for help if they don’t assume that people know to take the action necessary.
For example. I had to lookup a Youtube video on how to open the Dev Console to make that simple change to the sv_gravity value.
Most people don’t fiddle with these types of features. They just want to play the game and so they would not necessarily knowi how to open the console.
This little issues took many frustrating hours to resolve and the problem should not have been there in the first place.
I have all the Half-Life games but this issue definitely too the enjoyment out of this game for me.
I noticed that at least one other person had the same problem as me, but I didn’t see a reply that could have helped him.
It makes me wonder if he resolved the problem or just gave up as I was about to do.
I think that the developers of this game should publish a list of known bugs (and this is definitely a bug) and how to resolve them.
Just signed on to say thanks on this tip. Saved my weekend.
Perhaps a point_clientcommand entity could be used in the map at that section to ensure gravity is set to 600? While it might be more ideal to fix that bug, it would also ensure someone could get through if they changed gravity on their own for whatever reason.