Construction and Testing of a Vapor Sensor Based on Ion Mobility and Gas Flow.
NIOSH 1988 Nov:35 pages
In order to answer the need for low cost gas monitors for use in gas detection applications, a prototype sensor was built on the principle of ion mobility, and the performance of this prototype was evaluated. Ion mobility employed the difference in drift velocity in an electric field of ions formed from different substances. Due to its sensitivity, ion mobility has been used for the monitoring of a number of kinds of pollutants in air for a number of years. The technique was simple as separation of different ions depended on the difference in their drift velocities in air at atmospheric pressure. The ions were measured from the substance of interest at a narrow collector after they had traveled in a vertical direction under the influence of an electric field and in a perpendicular direction using air flow. It was anticipated that ions of different mobilities could be separated in this manner. The sensor functioned as predicted in a qualitative sense. At a given flow rate, response from the device was obtained over a given range of voltages, determined by the flow rate used. The device was very sensitive to flow parameters. By changing the flow pattern, response varied from that of no response to high levels of response. The use of either positive pressure or suction affected the magnitude and type of response. Higher flow resulted in not only higher sensitivity but also in wider peaks which reduced separation. Lower flows resulted in lower sensitivity but also in narrower peaks. Complete separation of acetone (67641) and benzene (71432) could not be achieved with the present configuration of the device.
NIOSH-Author; Air-quality-monitoring; Vapors; Gas-detectors; Hydrocarbons; Organic-solvents; Air-monitoring;
NTIS Accession No.
NIOSH, Cincinnati, Ohio, 35 pages, 7 references