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 December 1960. 1960;

Abstract: by A. Lieberman and J. Stockham Research Engineers Armour Research Foundation Chicago *1 liter-0 0353 cu. ft. 1 cu. ft.---28 32 liters THE CONCENTRATION and size distribution of airborne particles in a newly completed ultraclean precision assembly area were examined with an automatic particle counter utilizing light scattering as a means of detection. The range of particle sizes and the concentrations were related to the amount of activity in the area. With no activity in the area the particle concentration varied around 100 particles/liter.* These particles were between 0.5 micron and 4.0 microns in diameter. The concentration of particles above 1 micron was about 10/liter. With six people inspecting and repackaging parts the particle concentration rose to 314 particles/ Liter with particles up to 16 microns being present. There were about 120 particles/liter greater than 1 micron in diameter. The recovery time of the room from simulated normal operation was about 20 minutes and from extreme contamination about 1 hour. As indicated in the above summary the ultraclean room has become an essential tool for the precision instrument manufacturer. Elaborate and expensive ultraclean facilities are being provided in which to assemble and test precision parts. Recent articles (1 2) attest to the increasing interest in such facilities. Little is known of the actual dust levels in ... schö

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