A new instrument for short-term monitoring of ambient aerosol fine mass concentration has been developed based on a unique device called a Tapered Element Oscillating Microbalance (TEOM). The detector consists of a tapered hollow tube fixed at the wide end and holding an exchangeable filter cartridge at the narrow end. Air is drawn through the filter cartridge down the hollow tube. Particulates deposit on the filter cartridge. The tapered tube is maintained in continuous oscillation in a clamped-free mode whose frequency is accurately monitored. As particulates load on the filter cartridge, the frequency changes in relation to the mass added. A microprocessor-based electronics system collects and processes the data. Output is printed in a format consisting of time and aerosol concentration level in microgram/cu m. The time resolution of the instrument, i.e., the time required to measure an air pollution level of 10 microgram/cu m with an accuracy of 10% is 30 minutes. The inlet is equipped with a cyclone preseparator having a cutpoint of 2.5 micrometers (aerodynamic diameter), resulting in a system which provides a direct fully automated measurement of the fine mass concentration of ambient aerosol.

Caption title. "August 1981." "EPA-600/2-81-146." Microfiche.