The use of Wilson Exhaust Heads eliminates objectionable noise created by high velocity discharge of steam, air or other gases. They also offer protection from exhausted moisture by collecting and draining off liquids entrained in steam vapors. The Wilson Silent Exhaust Head – whether vertical or horizontal type – uses a reverse flow double expansion principle. The flow area is increased 1-1/2 times on the first pass to 4 times on the second pass through the unit. Through this expansion the speed of the exhaust is greatly reduced thereby eliminating objectionable noise.