Table 9.32.3.11.-A is based on the data listed in Table 9, “Friction Chart for Round Ducts,” Chapter 32, of the ASHRAE 1997, “ASHRAE Handbook – Fundamentals.” The allowable duct lengths listed in the Table have been calculated assuming the “equivalent lengths” of ducts are four times their physical lengths. The static pressure offset to account for building pressures is 10 Pa. Using Table 9.32.3.11.-A will generally result in very conservatively sized (i.e. larger) ducts compared to what would be achieved using the normal duct design procedures referenced in Subsection 9.33.4. Enthalpy recovery ventilators (ERVs) are a type of heat recovery ventilator and must therefore comply with the requirements of Article 9.32.3.12.