Gorton, No. 1, 3/8" Straight Air Eliminator, Steam Air Vent Valve, #1 3/8" air vent INSTALL one or more No. 1 Air Eliminators at end of the short main or the main running to the warm side of the building. INSTALL two or three No. 1 Air Eliminators at end of the long main or main running to the cold side of the building. Or, depending upon the size of the building, use a No. 2 Air Eliminator.