Evaluation of the Jarless Method for Cyclone Calibration in Occupational Air Sampling

The jarless cyclone calibration method is an appealing approach because it removes the need for calibration adapters and eliminates potential sources of error that result from poor or inconsistent seals in calibration adapters or calibration jar lids. The aim of this study was to perform a detailed review of the jarless calibration method by (1) examining the rationale behind the initial pressure drop range specified by the method and (2) evaluating the accuracy of the method in contrast to flow rate measurements in a well-controlled, jar protocol. Four types of respirable cyclones and two filter brands with samples from three separate production lots were considered as components of the sampling trains under consideration. Volumetric flow rate and pressure drop were measured under controlled conditions in a cylindrical jar designed for these determinations. The initial challenge pressure range evaluated in this study was modified based on cyclone type. The measured pressure drop fell within the modified range for all configurations considered, indicating the modified ranges were appropriate. The accuracy of the jarless method was then evaluated by comparing measured volumetric flow rates using different calibration methods for various cyclone, filter brand, and filter lot combination. The jarless method provided accurate calibration results utilizing the modified initial pressure drop ranges utilized in this study. Therefore, it is recommended the initial pressure drop range specified by the jarless method be modified to account for differences among cyclone types.