Assessment of real-time measurements of respirable dust and crystalline silica concentrations

Real-time measurements of Respirable Crystalline Silica (RCS) can significantly enhance the capability of workplaces in conducting timely risk assessment and monitoring. A new device has recently been launched (Trolex Air-XS, United Kingdom) for real-time monitoring of RCS based on light-scattering optical refractometry technology. This study aimed to examine its capability in determining concentrations of respirable particles in general and distinguishing RCS proportions from other particulates. Tests were carried out in a controlled environmental chamber using various dust samples with different RCS content, employing two other light-scattering-based devices (Fidas Frog (Palas GmbH, Germany) and TSI DustTrak DRX 8533 (Shoreview, Minnesota, USA)). The tests revealed that while Air-XS demonstrated strong temporal correlation to the particle concentration readings of Fidas, it tended to record significantly lower particle number concentrations, largely because it does not include the sub-1-micron particle range within its algorithm/sensor capabilities. This presents a significant limitation, as sub-1-micron-sized particles are significant determinants in the toxicity of respirable aerosols. This study also found that the Air-XS device was unable to distinguish crystalline silica from general particulate dusts, possibly due to the relatively low dust loading in the test environment. Some measurements with the Fidas and the DustTrak indicated environments that were nearing the Australian Workplace Exposure Standard concentration, suggesting further controlled testing is needed to thoroughly assess the Air-XS capability in detecting and measuring RCS. These findings indicate that while the Air-XS may serve as a real-time indicator of high concentrations of respirable particles, it is not a substitute for established RCS assessment methods. Further independent testing across various conditions is needed to confirm its accuracy, sensitivity, and reliability.