Development of A Low-cost Simultaneous Low Volume Air Sampler Controlled with Sonic Venturi

Abstract

This study presents the results of designing a low-cost air sampler for multi-component analysis of PM2.5. We developed a multi-channel air sampling device using sonic venturi (critical nozzle) that supplies a constant airflow rate of 16.7 L/min. The constant flow rate is achieved with a backpressure ratio of 0.8 or less with a nozzle diameter of 1.375 mm. The sampler halves the cost of comparable devices and simplifies the hardware by replacing the flow meters with critical nozzles. For quantitative evaluation, we measured the coefficient of variation (CV) of each component simultaneously collected five samples at various particulate matter concentrations. This sampler can use different types of filters such as polytetrafluoroethylene and quartz fiber filter at the same time. Meteorological conditions such as ambient temperature, relative humidity and atmospheric pressure did not seem to affect much the flow rate of the sampler. The CV of multi sample analysis for TSP and PM2.5 concentrations in all sampling periods were less than 10%. CV of multi sample analysis for most of the major inorganic elements being within the range of 15% or less shows that the precision is sufficient for reliable measurement. We believe that the low-cost multiple air sampler will be used world-widely, and it can contribute to many researchers in both developed and developing countries.