Mesh As Levels

Hello people, Loading meshes as levels seems a good idea, however... I load a mesh as a level- it contains simply the walls, floors and ceilings. I also have a first person camera which can navigate this small room. I would like to ensure the camera can only remain inside the room and not pass through walls or ceilings etc... Does anybody know how I can determine when the camera intersects with the mesh so that I may prevent it from moving further? Your assistance is appreciated.