A burner includes a motor driven blower, an air tube having an inlet end portion and an outlet end portion, a housing forming an air flow path between the blower and the air tube, a nozzle for spraying liquid fuel or orifice for dispersing gas toward the outlet end portion of the air tube and a conduit for feeding the fuel to the nozzle or orifice. An air flow control device and method enable air flow and pressure to be regulated at locations near the nozzle and between the blower and the nozzle. A contour of a throttle member of the burner is designed so as to achieve a prescribed pressure in a region between the throttle member and head of the burner over the range of the burner.