We are pleased to announce that on December 13, 2013, US Patent No. 8,597,391 B1 was issued for the Osprey Blue-Sky filter. First introduced at Index 2011, the Blue-Sky filter is a proven and safe filter design for those wanting the highest filtration efficiency available along with a reduced explosion risk. The filter consists of a primary rotary drum filter stage and a HEPA filter stage coupled to the outlet side of at least one passive filter stage.