Method and apparatus for real time asbestos aerosol monitoring

A real time asbestos aerosol monitor comprising:

• sampling means for obtaining an ambient air sample and providing said sample to a sensing chamber having a sensing zone;
• alignment field means for creating a constant alignment field at said sensing zone to align fibers in said sample at a first fiber angle;
• magnetic field means for creating a time-varying magnetic field at said sensing zone, said time-varying magnetic field being disposed at an angle relative to said alignment field, said time-varying magnetic field causing asbestos fibers aligned at said first fiber angle to oscillate between said first fiber angle and a second fiber angle;
• illumination means for illuminating said fibers aligned at said first fiber angle perpendicular to the axes of said fibers;
• and
• a detector for detecting light scattered by said fibers oscillating between said first and second fiber angles to produce a detector signal, said detector signal indicating whether an asbestos fiber has been detected.

A real time asbestos aerosol monitor comprising:

• sampling means for obtaining an ambient air sample and providing said sample to a sensing chamber having a first sensing zone and a second sensing zone;
• first electric field means for creating a first constant electric field at said first sensing zone to align fibers in said sample at a first fiber angle;
• second electric field means for creating a time-varying electric field at said first sensing zone, said time-varying electric field being at an angle relative to said first constant electric field, said time-varying electric field causing fibers aligned at said first fiber angle to oscillate between said first fiber angle and a second fiber angle;
• third electric field means for creating a second constant electric field at said second sensing zone to align fibers in said sample at a third fiber angle;
• magnetic field means for creating a time-varying magnetic field at said second sensing zone, said time-varying magnetic field being disposed at an angle relative to said second constant electric field, said time-varying magnetic field causing asbestos fibers aligned at said third fiber angle to oscillate between said third fiber angle and a fourth fiber angle;
• illumination means for illuminating said fibers aligned at said first fiber angle in said first sensing zone and said third fiber angle in said second sensing zone perpendicular to the axes of said fibers;
• a first sensing zone detector for detecting light scattered by said fibers oscillating between said first fiber angle and said second fiber angle to produce a first detector signal, said first detector signal indicating whether a fiber has been detected;
• and
• a second sensing zone detector for detecting light scattered by said fibers oscillating between said third fiber angle and said fourth fiber angle to produce a second detector signal, said second detector signal indicating whether an asbestos fiber has been detected.

A method of identifying on a real time basis asbestos fibers contained in an air sample comprising the steps of:

• obtaining an ambient air sample;
• passing said air sample through a sensing zone;
• exposing said air sample in said sensing zone to a time-varying magnetic field in order to cause airborne asbestos fibers in said sample to rotate in response to said time-varying magnetic field;
• illuminating said fibers;
• detecting light scattered by said fibers to produce a scattered light signal;
• and
• identifying from said scattered light signal asbestos fibers in said sample.

A method of identifying on a real time basis asbestos fibers contained in an air sample comprising the steps of:

• obtaining an ambient air sample;
• passing said air sample through a sensing zone;
• simultaneously exposing said air sample in said sensing zone to a constant electric field to align all fibers in said sample at a first fiber angle, and a time-varying magnetic field disposed at an angle relative to said electric field, said time-varying magnetic field causing asbestos fibers in said sample to rotate between said first fiber angle and a second fiber angle;
• illuminating said sample perpendicular to the axes of said fibers;
• providing a detector for detecting light scattered by said fibers, said detector producing a scattered light signal;
• determining from said scattered light signal whether a fiber has rotated in response to said time-varying magnetic field;
• and
• counting as an asbestos fiber any fiber determined to have rotated in response to said magnetic field.

A method of identifying on a real time basis asbestos fibers contained in an air sample comprising the steps of:

• obtaining an ambient air sample;
• passing said air sample through a first sensing zone;
• simultaneously exposing said sample in said first sensing zone to a first constant electric field to align all fibers contained in said air sample at a first fiber angle, and a time-varying electric field at an angle to said first constant electric field to periodically oscillate said aligned fibers between said first angle and a second fiber angle;
• illuminating said sample in said first sensing zone perpendicular to the axes of said fibers;
• providing a first sensing zone detector for detecting light scattered by said fibers in said first sensing zone, said first sensing zone detector producing a first scattered light signal;
• determining from said first scattered light signal whether a fiber has been detected at said first sensing zone;
• passing said air sample through a second sensing zone;
• simultaneously exposing said sample in said second sensing zone to a second constant electric field to align all fibers contained in said air sample at a third fiber angle, and a time-varying electromagnetic field at an angle to said second constant electric field to periodically oscillate asbestos fibers from said third fiber angle to a fourth fiber angle;
• illuminating said sample in said second sensing zone perpendicular to the axes of said fibers;
• providing a second sensing zone detector for detecting light scattered by said fibers in said second sensing zone, said second sensing zone detector producing a second scattered light signal;
• and
• determining from said second scattered light signal whether an asbestos fiber has been detected at said second sensing zone.