If the pipe you mean the gas line, it goes through the floor and connects to the main gas line under the trailer. If you get under the trailer you'll see the gas lines. You'd need to disconnect it, shut off the valve if there is one, and cap the line and double check for leaks, patch the hole in the belly and floor to keep cridders out. The vent in the floor probably opens up to vents in other places in the trailer (like the bathroom). If it is in the floor you'll probably have to settle for covering it up and forgetting about it, since removal would either mean removing the belly pan or floor.