Real-time Photoacoustic Measurements of the Mass Concentration of Respirable Crystal Silica Dust: Theory

Respirable crystalline silica (RCS) is an inhalation health hazard for mining and industrial work environments and must be monitored. We provide theoretical analysis of real-time measurements for determining RCS mass concentration without the use of filters by using photoacoustic spectroscopy. The suspended dust in the mine air can be continuously sampled by the photoacoustic instrument. A tunable quantum cascade laser is the light source, allowing for determination of interferences such as kaolinite, coal dust, and water vapor. The most useful spectral region is found to be between 11 and 13 mu m. Absorption by water vapor, and, to a lesser extent, carbon dioxide, in this spectral region has gaps that allow for quantification of the aforementioned dust species as well as a convenient check on the calibration of the instrument. This work brings photoacoustic measurement of aerosol to the mid infrared range where spectrally dependent light absorption can be used to quantify dust composition and mass concentration.

Automated summary

This research uses photoacoustic spectroscopy to monitor respirable crystalline silica (RCS) mass concentration in real-time without the need for filters. The study demonstrates that a tunable quantum cascade laser can be used as the light source to eliminate interferences from substances such as kaolinite, coal dust, and water vapor. By analyzing the spectral region between 11 and 13 micrometers, the composition and mass concentration of dust can be accurately quantified.