Vacuum cleaner and sealed filter bag assembly therefor particularly useful for filtering asbestos fibers from air

A filter bag assembly for a vacuum cleaner, comprising:

• a primary filter bag for collecting particulate material;
• a first inlet into said primary filter bag;
• said primary filter bag being otherwise sealed closed;
• said primary filter bag being permeable to air, but impermeable to particulate material to be collected in said primary filter bag;
• a shield around said primary filter bag;
• said shield being impermeable to both particulate material and to air;
• said shield having an open neck;
• a secondary filter shaped in the form of a bag having an open neck with said secondary filter bag having an outside serving as its inlet side and having an inside which is its outlet side;
• said secondary filter being sealingly attached at said open neck of said secondary filter to said shield at said open neck of said shield to seal closed said shield open neck, thereby to define an enclosure comprised of said shield and said secondary filter bag around said primary filter bag and in which said primary filter bag is wholly enclosed;
• said secondary filter being permeable to air but impermeable to the particulate material;
• a second inlet through said enclosure opening into said enclosure and also communicating with said first inlet;
• a tertiary filter positioned outside said enclosure at said shield open neck, being placed inside said secondary filter bag, and being in communication with said secondary filter for receiving outflow from said secondary filter;
• said tertiary filter is positioned at and is surrounded by said attached shield open neck and secondary filter open neck;
• at said shield open neck, at the attachment there with said secondary filter, elastic means being provided for drawing said shield open neck closed and also for closing said open neck of said secondary filter bag around said tertiary filter to provide a seal therewith.