Respirator users experience a physiological burden, one aspect of which is associated with breathing resistance from the filter. The current best practice of gas filters is to provide protection using 3adsorbent granule filled filters which, as the particle size decreases, have better adsorption kinetics, and hence longerbreakthrough times. However this comes at the price of an increasing pressure drop and hence greater breathing resistance. In this paper, adsorbent hollow fibres for use in respirator filters are presented as a potential alternative to the conventional granular cartridges. A comparison of hollow fibre and granular filter modules was carried out using scanning electron microscopy and dynamic ammonia challenge (800 ppm, 1 L/min). In addition the pressure drop was measured at flow rates between 0.5-5 L/min, and using these data,pressure drops at higher flow rates were predicted. The hollow fibres were demonstrated to compare favourably to a granular module of equal volume in terms of pressure drop, adsorption kinetics and breakthrough loading,although improvements still need to be made to hollow fibre breakthrough time, which is slightly lower than an equal volume pellet module as a result of the lower density of the hollow fibre filters. The qualities of hollow fibres will provide several options for novel filter design
