Development of a system to measure electric charge on industrially-generated aerosol.

A system for the measurement of net electrical charge on industrially-generated aerosol was designed, built, and tested. The system was then used to measure net change on welding fume and dust generated from sanding on fiberglass reinforced plastic (FRP). The measuring apparatus consisisted of a specially machined Faraday cap filter holder, a sensitive electrometer with a strip chart recorder, and an airflow system. Total mass of collected particles was determined gravimetrically. For the FRP samples, particle number was determined by scanning electron microscopoy; particle number could not be determined for welding fume because discrete particles could not be distinguished. Net charge was calculated in unites of elementary charges per unit mass of collected particulate or in elementary charges per particle as determined from scanning electron microscope (SEM) analysis. Net charge levels on welding fume were found to be of positive polarity and on the order of 10[8] elementary charges per milligram, while levels on FRP dust were negative and of the order of -10[9] elementary charges per milligram. On particles of FRP dust, there were approximately 400 elementary charges per particle. The major value of this study was in development of a measurement system for determination of net charge levels on aerosol. This is an important first step in development of a system for measurement of total electric charge on aerosol, which is more closely associated with biological effects in terms of increasing lung deposition of particulate, effects on particulate sampling in industrial environments, and effects on particulate control strategies