Abstract: A pulse combustion heater is described and includes a combustion chamber and at least one exhaust pipe forming a resonant system with a chamber. In one aspect of the invention, the combustion chamber has an internal cavity of flattened spherical shape which causes combustion gases returning to the combustion chamber to flow into said cavity in a double toroidal flow pattern. In another aspect, the apparatus has an exhaust system which includes a primary exhaust pipe of a length selected so that combustion of gases is at least substantially complete before the gases leave the pipe. The pipe terminates at a manifold to which is connected a plurality of heat exchange coils of helical shape from which heat is transferred to a fluid circulated around the coils.