[EN 12792:2003, 394]:means intended to increase the natural frequency of duct walls in order to minimize the possible effects of vibration.

[AIVC, Air infiltration and ventilation glossary, 1992]:spoiled, impure or polluted air.

[ASHRAE 62.1]:the total volume of an occupiable space enclosed by the building envelope, plus that of any spaces permanently open to the occupiable space, such as a ceiling attic used as a ceiling return plenum.