The aerodynamic behaviour of long aspect ratio nylon fibrous particles has been investigated experimentally while settling in air under super dilute conditions without any influence of secondary flows and at fibre Reynolds numbers of 0.5-2 based on fibre diameter. A method for laser-based measurement of the orientations and velocities of fibrous particles is also presented. The experimental apparatus employs a two-dimensional Particle Tracking Velocimetry (PTV) to calculate orientation and velocity based on the two end-points. The controlling length scale in the relationship between Reynolds number and drag coefficient was investigated and the equivalent diameter of settling fibre in air was reported. Finally the influence of volume fraction and fibre straightness were assessed. Crown Copyright .(C) 2012 Published by Elsevier B.V. All rights reserved.