Capable of capturing particles invisible to the naked eye,ATEX HEPA (High Efficiency Particulate Air) Cartridge Filter meets industry standards for HEPA air filtration by providing filtration of 0.3 microns @ minimum of 99.97% efficiency. Ideal for working with allergens, powders, and superfine particles. Grounding strap provides electrical continuity for ATEX compliance. Cloth Pre-Filter Bag provides extra stage of filtration extending the life of the cartridge filter. Fits Guardair ATEX 55 and 30 Gallon Drum Vacuums.