The Building Regulations require ductwork leakage testing, with implications for designers, installers, and maintenance contractors.
Air leakage from ducted distribution systems is an important consideration in the design and operation of ventilation and air conditioning systems. A ductwork system that has limited air leakage, within defined limits, will ensure that the design characteristics of the system can be maintained. It will also ensure that energy and operational costs are kept to a minimum.
Ductwork airtightness levels can be measured by ductwork pressure testing, usually involving temporarily connecting a duct leakage tester to pressurise the ductwork including duct-mounted components. Air flow through the pressurizing device creates an internal, uniform, static pressure within the ductwork. The aim of this type of measurement is to relate the pressure differential across the ductwork to the air flow rate required to produce it. Leakage testing should always be done under positive pressure even when the ductwork is to operate under negative pressure. This is because, if a duct under a negative pressure fails a leakage test, it is impossible to identify the leakage paths.
Generally, the higher the air flow rate required to produce a given pressure difference, the less airtight the ductwork.