I have an oil furnace. Beside my furnace is a 4 or 6 inch metal pipe that brings fresh iair straight into my furnace room. What is the purpose of this? Can it be blocked? It brings in air from our cold Canadian winters into my house. This must make heating my home more expensive and the electric water heater is 4 feet away. If it is a carbon monoxide problem, can I just get a detector so as not to have cold air coming into my house. And will putting an insulating blanket on my water heater make much of a difference in my water heating costs?