It is recommended to protect the fittings from contamination. Fittings with circular connections can be fitted with dust caps for this purpose. Fittings with rectangular connections can be covered with foil or fitted with dust caps. If the dust caps and/or foil are only removed when the relevant connection is actually connected to the air duct system, the degree of contamination is minimised.
To be able to inspect the installation properly, sufficient inspection hatches are required. The hatches should be fitted in the right place and be of sufficient size. Preference is given to components with inspection hatches. In addition to the doors for components requiring service which are not fitted with an inspection hatch, it is recommended that additional hatches are fitted in shafts, technical rooms and floors. The hatches must be easily accessible and clearly indicated on the drawing by the coordinating party. NEN-EN 12097 should preferably be used as the basis for the inspection facilities.