J Med Assoc Thai 2000; 83 (2):117

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Personal Respiratory Protective Devices: Efficacy of Millipore and Whatman Filters
Tanpowpong K Mail

A Millipore filter with 0.22 Jlil1 pore size and a Whatrnan grade 1 filter with > 11 IJm
particle retention were used to capture laser smoke particle mimic atmospheric suspended
particulate matter. The experiment was conducted at the Department of Otolaryngology in Rama-
thibodi Hospital from April 1996 to October 1997. The laser smoke particle evacuator with
rotameter created an air flow rate of 15 Vmin through the filters. The mean and standard deviation
of the laser smoke particle count under high power optical microscope in a 10 Millipore filter and
a 10 Whatman filter were 411,327.6 +/-13,325.0 and 290,453.0 +/-28,409.8 respectively, 29.4
per cent different. Laser smoke particle size distribution in both filters under eyepiece micro-
meter was: 1 to 10 j..lm in Millipore (99.0%) and in Whatman (96.2%), 1 to 5 j..lm in Millipore (77.1 %)
and in Whatman (77.6% ), no laser smoke particle larger than 17 Jlil1 was detected. The Millipore
filter ruptured when the air flow rate was greater than 15 Vrnin. The Whatman filter was suitable for
evaluating filtration efficacy of various personal respiratory protective devices in a high air
flow rate condition.
Key word : Filter, Suspended Particulate Matter, Laser Smoke Particle, Prevention

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