A housing with a first end wall and second end wall with a first baffle and second baffle spaced apart and positioned between end walls with a cover attached to form a first chamber, an intermediate chamber and a third chamber. An intake tube is inserted through the first end wall, first baffle and second baffle to terminate at an exit end in the third chamber. An exhaust tube is inserted through the second end wall, second baffle and first baffle to terminate at an intake end in the first chamber. The intake tube and exhaust tube each have openings in an intermediate tube wall. The exhaust tube has openings in a second tube wall portion. There is an intermediate port in the first baffle. A threaded shaft of a valve is threadably engaged in a fitting attached in the second end wall to be positioned opposed the exit end.