A new mode of soil failure can renew filtration surfaces in a bed of granular solid held in place by louvers mounted to provide a tall, narrow "panel bed" filter. A sharp "reverse" puff of gas (or pulse of a liquid), at sufficient intensity and not too long duration, produces a body movement of the solid capable of causing it to spill in a substantially uniform amount from each fluid-entry surface of the bed's face. The new phenomenon places the panel bed in contention to filter dirt from a gas (or from a liquid) wherein an accumulated filter cake becomes the primary locus for dust capture, by a sieving mechanism. (c) 2005 Elsevier B.V. All rights reserved.