Tunnel Factory Escape

There was a engineer who came to visit the Tunnel Factory. The engineer was there because he needs to inspect the facility and the building, if its needed to be repaired. When he was there and busy inspecting the place, he accidentally locked himself in one room. He shouted for an help but his echoes keeps coming back without an reply. Find the clues and use the hints and solve the puzzles for him to escape from that one room.