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A measurement system for microelectronic clean rooms to measure
ultrafine particle size distribution in the range of 0.002 to 0.2
micrometers is provided which includes four screen diffusion stages
each connected in series with a condensation nucleus detector. The
input to each screen diffusion stage is connected to a localized
area to be measured, and the output of each condensation nucleus
detector is connected to a vacuum system which simultaneously draws
particle bearing air through the four channels. The output signals
of the condensation nucleus detectors present particle size
distributiion. In one embodiment of the present invention, one or
more optical particle detectors are connected in parallel with the
diffusion stage-condensation nucleus detectors to expand the
distribution measurements to larger sizes. Other embodiments
inclulde a manifold probe to probe a localized area, an alarm
system actuated when particle levels exceed a predetermined level,
and a manifold assembly to minimize vacuum lines passing through
the walls of the microelectronic clean room.