CleanSpace particulate pre-filter is suitable for protection against airborne particulates (dust, mists, and fumes); the pre-filter is designed to remove coarse particles and enhance the life of the particulate P3 filter on PAF-0037 and combined filters; the pre-filter should be changed after each use; important: when selecting a CleanSpace filter, please consult a health and safety specialist for advice on the appropriate respiratory equipment and filter use; compatible with all CleanSpace PAPR power units; easy and quickly fitted and removed from the power unit; sold in a pack of 20 pcs.