Air filtering apparatus

Claim 1

An air filtering apparatus comprising a chamber having an inlet and an outlet, a prefilter panel disposed across said chamber inlet, a HEPA type filter panel disposed across said chamber outlet, dividing means intermediate said prefilter panel and said HEPA type filter panel for dividing said chamber into adjacent first and second subchambers, said dividing means having an opening through which air may pass from said first subchamber into said second subchamber, blower means intermediate said prefilter panel and said HEPA type filter panel for forcibly blowing air from said first subchamber through said dividing means opening and into said second subchamber, whereby air will be drawn through said prefilter panel into said first subchamber and will be forced into said second subchamber and exhausted through said HEPA type filter panel, pressure responsive indicator means responsive to a predetermined increase in pressure in said second subchamber for indicating when said HEPA type filter panel requires changing, said blower means including an electric blower motor, the speed of which may be varied by varying the voltage applied thereto, a voltage supply circuit, and means for varying the voltage applied by said circuit to said blower means, said voltage varying means including switch means connected to said voltage supply circuit and operable in two alternative positions for supplying two alternative voltages for operation of said blower motor at two alternate speeds, one of which is sufficient to generate pressure conditions within said second subchamber sufficient to actuate said pressure responsive means if the HEPA type filter panel requires changing, control means responsive to a predetermined signal for effecting movement of said switch means from one of said alternative positions to the other, signal applying means operatively connected to said control means for applying an actuating signal to said control means, said signal applying means including radio frequency receiver and signal circuit means operated by said receiver in response to receipt of a predetermined transmitted frequency for applying an actuating signal to said control means, and means for generating the predetermined radio frequency for actuating said radio receiver, whereby said blower means may be remotely controlled to test the condition of said HEPA filter panel.