Abstract: A combustion air bubble chamber having an inner surface defining an hourglass-shaped column of water and bubble holes located at the bottom of the chamber outwardly of the waist so that bubbles rising from the holes contact the converging inner wall of the lower part of the chamber, are reduced in size, flow along such wall around the waist and outwardly along the diverging wall of the upper part of the chamber and are released from the upper wall to rise to the top of the water. These bubbles are effectively humidified as they rise from the bubble holes to the top of the water. Vapor drawn from the head space above the water is flowed to a burner combustion chamber for improving combustion efficiency.

Abstract: The combustion efficiency of oil or gas-fired furnaces is increased by flowing air through a bubble chamber and drawing the treated output into a stream of air directed into the combustion chamber so that the stream of air mixes with the flame.