[EN 13141-4:2021, 3.11]: [EN 13141-7:2021, 3.1]:leakage to or from the air flowing inside the casing of the ventilation unit to or from the surrounding air.

(See air infiltration) )

[EN 12792:2003, 236]:in-flow or out-flow through cracks in a specific part of a ventilation or air conditioning installation, due to pressure differences