This booklet is the work of Gerry Gill and Steve Pajek, two very knowledgeable contractors from Ohio. You can learn more about them HERE. Gerry and Steve did this exhaustive, original research on steam air vents, both old and new, and steam traps (which must vent air before they can trap steam). The result of their work is this remarkable booklet that gives you a way of balancing one- and two-pipe steam systems. You'll be doing what many say can't be done.