Air gas furnace systems must uphold standards set in place by the ACCA (Air Conditioning Contractors of America). Standards are outlined in manuals authored by the ACCA. Manual D can be referenced to determine a gas air furnace heating system's proper ductwork design for the space it is employed to heat.
A gas air furnace heating system performs more efficiently with properly installed and sealed ductwork. Draw bands used should have a minimum tensile strength of 50 pounds and a 165-degree Fahrenheit temperature rating. Water-resistant, non-toxic sealants should be employed in a gas air furnace duct system to increase efficiency. Proper ductwork and fittings are made up of galvanized metals.
All components of a gas air furnace's ductwork system must meet minimum performance temperature ratings. They must meet minimum flame spreading ratings and smoke development ratings. Ductwork should never come in contact with plumbing lines, conduit lines or any other metal fixture.