Carbon Filter Test Bed Monitoring: Part 1. Evaluation of a SAW Chemical Sensor.
Interim rept. Oct 96-Sep 97,
NAVAL RESEARCH LAB WASHINGTON DC SURFACE CHEMISTRY BRANCH
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The military currently uses a large number of single-pass, fixed bed carbon filter elements in their personal and collective air purification systems. A means of measuring the residual adsorption capacity of in-service carbon filter elements is virtually nonexistent. As a result, filter elements are replaced after a period of service time whether they are still functional or not. To address this deficiency a miniature surface acoustic wave SAW chemical sensor has been evaluated as a monitor of filter bed condition. In the initial effort reported here, a polymer coated SAW sensor has been utilized to monitor the progression of a nerve agent stimulant, dimethyl methylphosphonate, through a filter test bed filled with carbon adsorbent. Studies were carried out with the SAW sensor embedded at the end of the filter bed to monitor the effluent gas stream, and in the middle of the filter bed. In either position the real-time frequency response of the SAW sensor was monitored as a function of time. Performance of the sensor and the breakthrough characteristics of the filter bed were studied as a function of the relative humidity of the air stream and the SAW sensor position in the te5t bed. With minor modifications the commercial SAW sensor was found to perform well in the filter bed environment. The polymer-coated SAW sensor was able to successfully follow the progression of DMMP vapor through a filter test bed, from low to high vapor concentrations.
- Line, Surface and Bulk Acoustic Wave Devices
- Pumps, Filters, Pipes, Tubing, Fittings and Valves