Airborne nanoparticle sizing by aerodynamic particle focusing and corona charging.

摘要

Over the years, there have been increased indications that fine and ultrafine particles present in the air can cause significant health risks. A few instruments employing different techniques have been developed to measure real-time particle size distribution (PSD) in the air. Some of them can measure the PSD with high efficiency down to about 2.5 nm in diameter. However, existing techniques are quite expensive and sometimes require employment of an expendable and flammable fluid. In general, none of the conventional technologies allow combining high efficiency, easy access and low cost.;In the present research the overall meterage system of the prototype was improved by determining the operational conditions which avoid particle generation. In addition, it was found that the corona charger section also filtered particles. Experimental investigation was introduced and an empirical correlation describing particle filtration rate was developed. Moreover, the theoretical part of the prototype operation was revised and corrected. It was found that the new apparatus could perform measurements without employing conventional techniques such as SMPS for its calibration. A comparison was made between the prototype and the SMPS using generated test particles in the size range below 300 nm (sodium chloride aerosol) to confirm accuracy of the developing apparatus' operation.;Previous studies have shown that a new apparatus based on aerodynamic particle focusing and corona charging techniques produced good agreement in particle sizing and counting with the conventional one for particles larger than 60 nm. However, it was suggested that the corona charger generated particles less than 60 nm, and therefore could not be used directly in the range below 60 nm.