Any air leakage from the air transport route must be limited in order to minimise the energy consumption of the air conditioning system. The basic principle is that if the air ducts meet the airtightness requirements, then airtightness requirements must also be set for the intermediate fittings. These airtightness requirements are the same as those internationally agreed on in the NEN-EN 1751, 13180 and 15727 (depending on the type of fitting).
In the Quality Guide the standard to be applied for each fitting is mentioned. If not indicated otherwise in the specifications, Luka uses class C as the airtightness requirement. Fittings must therefore at least comply with airtightness class C. Fittings with circular connections with rubber "safe" seals are preferable, as they make it possible to meet the airtightness requirements for the entire air transport route more efficiently. The use of safe seals does not increase the airtightness of the fitting itself.