Skc, Inc.

Peter M Hall

Donald Lee Smith

Saulius Trakumas

Charles A Krajewski

Charles W Nachreiner

A gas sampler includes an impact disc for removing larger particles from a gas flow drawn by a pump and a filter for capturing smaller particles, also positioned in the flow path. The sampler is conveniently dissembled and reassembled to remove and replace the impact disc and the filter. Particles removed, especially on the filter, may be observed or analyzed. The impact disc may be coated with an oil or other viscous substance to enhance its ability to retain larger particles. The flow path may be entirely annular after striking the impact disc&#x2014;that is, around the outside of the impact disc but a portion of the flow path may proceed directly through a central aperture in the impact disc after striking it.

Modular particulate sampler

An air sampler is designed for a predetermined flow rate. The air flow is admitted to at least two impactors operating in parallel. Preferably the inlet nozzles and the outlet orifices of each impactor are sized to achieve predetermined cut-off sizes of particles; preferably the composite curve of all the impactors will mimic a predetermined particle sampling efficiency curve.

Air sampler with parallel impactors

A constant flow of air through a personal air sampler is provided regardless of changes in the air flow path, by altering the pump speed as a function of the power taken by the pump. The characteristics of the pump are precalibrated to provide a constant used together with the square of the voltage appearing across the motor armature coils (applied voltage minus back Emf), which reflects the power currently used, to adjust the motor speed and thus provide a constant flow of air under changing conditions of resistance.

Air sampler with compensating pump motor speed

A passive air sampler is designed to facilitate emptying granular or particulate adsorbent from it directly into a thermal desorption tube or other vessel for use in an analytical instrument. The preferred form has an adsorbent container in a conical or funnel-like shape.

Passive sampling badge

A method for calibrating a personal air sampler. A desired flow rate is set, the actual rate measured and recorded through a plurality of runs, the results are automatically averaged and compared to the desired flow and the pump is automatically adjusted accordingly. The process may be repeated for a plurality of selected flow rates, and a best-fit curve computed to cover the entire range. Stability is tested by a series of sets of runs to determine erratic behavior, and an overall calibration is conducted by performing such a series of runs at each of several set point flows.

Method and apparatus for calibrating personal air samplers

Method and apparatus for calibrating gas samplers

An air or gas sampling device utilizes a small tube calibrated under isothermal conditions. The relationship of pressure at the input end of the tube to flow is plotted and stored in a microprocessor for comparison with pressure monitored during sample pumping. Pulsations in flow caused by the air or gas pump can be neutralized by a damper comprising a small chamber having a diaphragm for one wall.

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Venetia, PA, United States of America

Peter M Hall