Review of Filters for Air Sampling and Chemical Analysis in Mining Workplaces

Abstract

This review considers the use of filters to sample air in mining workplace environments for dust concentration measurement and subsequent analysis of hazardous contaminants, especially respirable crystalline silica (RCS) on filters compatible with wearable personal dust monitors (PDM). The review summarizes filter vendors, sizes, costs, chemical and physical properties, and information available on filter modeling, laboratory testing, and field performance. Filter media testing and selection should consider the characteristics required for mass by gravimetry in addition to RCS quantification by Fourier-transform infrared (FTIR) or Raman spectroscopic analysis. For mass determination, the filters need to have high filtration efficiency (≥99% for the most penetrable particle sizes) and a reasonable pressure drop (up to 16.7 kPa) to accommodate high dust loading. Additional requirements include: negligible uptake of water vapor and gaseous volatile compounds; adequate particle adhesion as a function of particle loading; sufficient particle loading capacity to form a stable particle deposit layer during sampling in wet and dusty environments; mechanical strength to withstand vibrations and pressure drops across the filter; and appropriate filter mass compatible with the tapered element oscillating microbalance. FTIR and Raman measurements require filters to be free of spectral interference. Furthermore, because the irradiated area does not completely cover the sample deposit, particles should be uniformly deposited on the filter.

Elemental Analysis of Particulate Matter by X-Ray Fluorescence Methods: A Green Approach to Air Quality Monitoring

“…It is important to select the appropriate substrate for PM collection based on the specific requirements of the study, the desired particle size range, the nature of the particulate matter, and the compatibility with subsequent analytical techniques. Substrate materials include cellulose, glass fibre, quartz fibre [45,46], polytetrafluoroethylene (PTFE) [47,48] greased quartz reflector [49,50], mixed cellulose ester, greased aluminium foils, or Si wafer [51]. The most widely used collecting substrate for EDXRF is a filtering membrane, offering a high capture efficiency, allowing for the collection of a wide range of particle sizes.…”