Abstract: A steam generator including a steam chamber defining an enclosed fluid chamber with a plurality of tubes passing through the steam chamber, a combustion chamber defining a closed fluid chamber and an air channel coupled to a burner, and a heat transfer section defining a closed fluid chamber and an air passage in fluid communication with a vacuum source, in which the burner generates a heated air mixture, the vacuum source draws the heated air mixture from the combustion chamber air channel, through the steam chamber plurality of tubes and through the heat transfer section air passage so as to heat fluid passing through the heat transfer section, the steam chamber and the combustion chamber fluid chamber.