Huh thats a new one... I just ran through the game to check it out. If your in the secret vent inside the house and can move after crouching you just have to hit the wall you came in trough (it'll be invisible from your view)
...But... if your in the lab with all the dead bodies... im sorry to say your at of luck there... this is something i didn't know about and im really sorry that you had to find it in this way... but thank you for playing this game it means a lot.