A radiant tube heater assembly includes a housing containing a blower and a burner, which is aligned with an opening in the housing through which a flame and products of combustion flow into a U-shaped burner tube. The closed downstream end of the burner tube is in close proximity to the housing. In order to prevent or reduce the likelihood of the products of combustion entering the blower, an exhaust tube is mounted in a downstream leg of the burner tube and extends outwardly through the U-shaped outer end of the tube remote from the housing.