Abstract: A fire or explosion suppression system provided with a source of pressurized suppressant and an apertured release suppressant nozzle which extends into the area protected by the system is provided with a cover unit which prevents the nozzle from becoming clogged or impeded by solid materials present in the protected zone. The cover unit that envelops the nozzle is of elastomeric material and has four internal grooves defining lines of weakness which present a cross-pattern. Upon release of the suppressant, the cover unit ruptures along the lines of weakness whereby the petal-shaped areas of the unit defined by the grooves open up for free flow of suppressant therepast.