What is a gas-fired natural draft boiler? How do I know if I have one?
Residential boilers heat water that is typically circulated through the house by means of piping and radiators. Gas-fired means either fuelled by natural gas or propane. Natural draft means that the combustion products from the boiler exit from the house through a chimney or metal vent without any assistance from fans (i.e. from the natural buoyancy of the heated combustion products (fumes).