... weight, comfortable in wearing, airtight, high filtrating efficiency, huge air flow, easy in operation with remarkable positive pressure, service life ... 3μm 2) filtrating efficiency :99.97% ,3) air flow: 170-300L/Min, adjustable air flow (clockwise regulate big flow and anti-clockwise ... can supply power 6 to 8 hours consecutive operation, If air flow regulate maximum, the lithium battery can work for ...