Detection of airborne particles by condensation method

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Condensation nucleus counter (hereafter CNC), a detector for ultra-fine aerosol particles by condensation of vapor onto the particles, which plays an important role in detection and sizing of aerosol particles smaller than 0.1) mum in diameter, has been studied from the view points of fundamental analysis to improve its performance and application techniques combined with it. The results obtained are as follows.1. Fundamental analysis for improvement in performance of CNCHigh flow rate (2.8 1/min and 14 1/min) mixing type CNC's were developed and evaluated the particle counting efficiency as the function of supers aturation formed in CNC's at various, operating conditions. it was found from the calculation of supersaturation and experiment that high counting efficiency was attained at the supersaturation as close as to the critical one derived from the classical nucleation theory proposed by Becker-D6hring-Zeldvich, where homogeneous nucleation was initiated. This fact gave us a theoretical criterion for developing high performance CNC'S. The performance of the CNC thus finally developed is summarized as follows : particle counting efficiency of 100% for particles larger than 10nm, efficiency of 60% for 5nm particles, and the flow rate of 14 I/min which is 50 times as high as existing CNC's were attained.2. Application techniques using CNCA new cumulative type electrical mobility analyzer combined with high flow rate (14 1/min) CNC above developed has been successfully developed, and it was found that the analyzer was capable of size analysis for atmospheric and room aerosol particles ranging 5-100nm in diameter. other application techniques using the prototype CNC include those for testing method of membrane gas filters having very high collection efficiency (99.9999999%), evaluation of deposition velocity of ultra-fine particles onto surfaces, and those for detecting bacteria and soluble impurities in water by aerosolizing method.