IMPROVED CONTROL AND MEASUREMENT OF CLEAN ROOM CONTAMINATION

During visits at numerous AFLC depots, several methods of indirect determination of the 0.5 micron particle contamination level in class 100,000 clean rooms were observed. These were predicated on an assumption that a statistical relationship existed between 0.5 and 5.0 micron particulate densities. The project resulted from questions as to the accuracy and reliability of such techniques. Several approaches to an indirect estimation of the 0.5 micron count for manual sampling data are presented. The evaluation revealed the following: (1) Projection methods are of little value. (2) The highest accuracy of the methods evaluated is attained by means of experimentally determined ratios which could be used for routine monitoring. (3) For a room in which the particle count is near the operational limit, i.e., the Air Force Standard Clean Room Curve (AFSCR Curve), the only meaningful determination of the 0.5 micron count is by actual direct measurement utilizing electronic means. (Author)