Fibrous filters are a well established technology for the removal of fine particulates (<10 mu m) from gas flows at high efficiency and low pressure drop. The behaviour of these materials in their clean state is well understood, but their behaviour as they become loaded with particulates has received surprisingly little attention; especially when one considers that a fibrous filter is in its clean state for only the tiniest fraction of its lifetime. At the Loughborough University of Technology a number of projects have been, and are being, undertaken where the dynamic characteristics of fibrous filters are studied. The paper reports on recent advances in this field made at Loughborough, and elsewhere, and suggests some further studies required.