Dust elimination and dust accumulation problems related to entrainment of man-made mineral fibres (MMMF) in spaces from continuous sources, such as interior materials or mechanical ventilation systems, are discussed. Ventilation rates lower than 4 ACH have virtually no effect on fibres larger than 10 μm which have maximum potential for causing skin, eye and possibly upper airway irritation. These fibres are removed almost exclusively by sedimentation. They are then available for skin contact, transfer via the fingers to the face and eyes or local redispersion unless they are constantly and efficiently removed by cleaning. Even the load from a weak source may be of importance if accumulation is allowed to occur. The settled fibres may then be the cause of complaints about the indoor environment and quantification of MMMF on surfaces should always supplement determination of airborne fibres.