unable to open airlock

I have downloaded a demo version of Doom3. I am only at the point where I have to walk outside for the first time through the airlock. I have not encountered any bad guys yet. The door won't open and I can't find any keypads,switches,etc. Can someone help? Thanks,
Rod.

Are you inside or outside?
There is a panel on the airlock (on both sides) and in the airlock itself.

I am inside. I have just come down stairs and a soldier has just told me to go outside via the airlock. The door looks like a metal garage door. I don't see any keypad. i pushed on the door, the sides, a console in the center of the floor and the airlock sign on the opposite wall.Thanks,
Rod.

Try posting a pic. It'll help us figure out what you're talking about.

To open there door (not sure if you've done so yet) all you have to do is click into the console with the words "Cycle Airlock" on it. It's right on the door itself, which is cylindrical and protrudes from the surrounding wall.

If you're already inside the airlock then again there should be a console on your left (when facing the second door, your back to the guard) which also says "Cycle Airlock".