Prolonged inhalation of respirable coal mine dust can cause coal workers pneumoconiosis. Accurate measurement of respirable dust is crucial to successfully reducing dust exposures and eliminating disease. The need for a new type of coal mine dust sampling device is evident. The operating principle uses a replaceable filter cartridge mounted on the narrow end of a hollow tapered tube. The wide end of the tube is fixed.
Air passes through the filter and down through the tube to a pump.
The tapered tube with the filter on the end is maintained in oscillation. The oscillation frequency depends on the characteristics of the tube and the filter mass at its end. As dust collects on the filter, the mass change is sensed as a frequency change in the oscillation of the tube. The mass of dust collecting on the filter is then determined directly. Since frequency can be measured accurately, the method can measure very small mass changes.