It is essential that flats, apartment block or any other 'multiple-dwelling' building should have their ducted ventilation systems inspected regularly, as air quality plays a huge role in maintaining the good health of inhabitants. Information regarding the American experience in multiple dwelling condominiums is related here: http://cooperator.com/articles/2696/1/A-Breath-of-Fresh-Air/Page1.html#! The same applies to social housing and luxury apartments with ducted extract or balanced ventilation throughout the UK and Ireland.
Dirt in ductwork can pose a fire risk (hidden combustion load), hygiene/odour problems and has been shown to reduce ventilation efficiency with knock-on effects for mould and contaminant control in the served area.
Call VSS on 0333 500 8368 to arrange an inspection today.