Chaffoteaux fan motor assembly also known as a centrifugal fan, as gas burns in the combustion chamber, harmful gases are released and the fan pushes the waste gases via a pipe known as a flue. This is a large pipe that's specific to the central heating boiler. The boiler will have a vertical flue going through a roof or a horizontal flue going through a wall. This is what takes hazardous gases from your property. For any reason, the fan ceases to function, the boiler will not work.