A laboratory duct leakage measurement system was developed and applied to measure the total leakage rates and the leakage of the joints and seams. Leakage measurements were made on 6 inch (150mm) and 10 inch (250mm) round and 14 inch by 6 inch (350mm by 150mm) and 22 inch by 8 inch (560mm by 200mm) rectangular sheet metal ducts for both positive and negative internal pressures. Average results for all the test ducts plus detailed data for three representative duct types are given. Sketches of the seams and joints tested are shown. The leakage rates for individual sites were determined by measuring leakage with and without sealing specific sites. For example, the joint leakage was determined by measuring the leakage with the seams sealed. Similarly, the seam leakage was determined by measuring the leakage with the joints sealed. The seam leakage could also be estimated by subtracting the measured joint leakage from the measured total leakage.

KEYWORDS: year 1995, ducts, leaking, measuring, pressure, welts, joints, pressure difference, calculating, testing, geometry, comparing