Part II Here's a special report from Armour Research Foundation on airborne particle size and concentration in white room areas as recorded by automatic particle counter

Journal/Book: Automatic Techniques of Airborne Patricle Counting AIR ENGINEERING JANUAR 1961. 1961;

Abstract: by A. Lieberman and J. Stockham Research Engineers Armour Research Foundation Chicago Summary and Conclusions An automatic particle counter was used to examine the atmosphere in a newly completed ultraclean room. At the time of the test the room was not being used routinely but simulated operations were performed to study their effects on the particle count. At zero activity the particle concentration in the room varied near 100 particles/liter of air. This concentration included submicron particles almost exclusively. The concentration of particles larger than 1 micron was approximately 10/liter. No particles larger than 4 microns in diameter were found. These values can be compared with those found in dustfree hoods of the type in general use which usually emit no particles larger than 1.5 microns. The zero-activity background concentration varied from day to day. These variations are probably a result of minor changes in room cleaning procedures in atmospheric conditions particularly relative humidity and in air cleaning and flow. In addition to the day-to-day changes in particulate concentration there were small (about 10 percent) variations in concentration from minute to minute. No explanation is offered for these variations except to comment that such variations are observed in normal air parcels. ... schö

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