Help unlocking door in Research Room

[toretorden]

Here's how I did it :

Spoiler below!

The first thing I did was to turn the valve when the infected came at me so that the box was up there. Then I lured the infected back into the room it came from and shut the door on it. By the time it was out, I was at the other end of the room, waiting for the right moment to pull the lever. As it came onto the rectangle on the floor underneath the box, I yanked the lever .. problem sorted!