. Transactions - American Society of Heating, Refrigerating and Air-Conditioning Engineers. tter has a higher filtering efficiency, buta higher resistance to flow of air through it and increases the work ofsampling. It cannot be purchased in size so was prepared by screeningXXX pulverized sugar; 60 per cent is 48 to 150 mesh size. Determining Dust in Air, Fieldner, Katz and Longfellow III Fig. 2 pictures a sugar tube attached by a non-collapsible rubber hose tothe foot pump for drawing the air. The pump is a lungmotor de-signed for resuscitation purposes but modified by changing the valves sot
. Transactions - American Society of Heating, Refrigerating and Air-Conditioning Engineers. tter has a higher filtering efficiency, buta higher resistance to flow of air through it and increases the work ofsampling. It cannot be purchased in size so was prepared by screeningXXX pulverized sugar; 60 per cent is 48 to 150 mesh size. Determining Dust in Air, Fieldner, Katz and Longfellow III Fig. 2 pictures a sugar tube attached by a non-collapsible rubber hose tothe foot pump for drawing the air. The pump is a lungmotor de-signed for resuscitation purposes but modified by changing the valves sothat it draws air through the sugar on the upstroke and discharges onthe downstroke. It is constructed of nickeled brass and aluminum, andweighs 11 lb. About 20 to 22 strokes are required per cu. ft. of air;calibration is accurately done with the entire sampling apparatus con-nected to a gas meter at the intake, as pictured in Fig. 7. The manometershown was used in experiments for indicating suction. A counter is at-tached to the pump for registering the strokes. Approximately 15 cu. FIG. 7. SUGAR TUBE AND FOOT PUMP ATTACHED TO GAS METER FOR CALIBRATING of air is used for each sample requiring about 15 minutes is laborious but after some practice a sampler does not become over-tired by it. A motor-driven pump has been designed for use where elec-tric power is available. CONCLUSIONS FROM TESTS OF SUGAR TUBE FILTERING EFFICIENCIES A detailed description of the tests made to determine the efficiency ofsugar tubes as filters will be published later by the Bureau of of the conclusions drawn from these tests are as follows: 1. Filtering efficiency of sugar tubes increases with increase in diameterof the tubes. Various tests made with tobacco smoke to comparetubes of lyo and 2yi in. diameter showed efficiencies between 23 and60 per cent with an average difference of 13 per cent in favor of thewider tube. 112 Transactions of Am. Soc. of Engineers
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