The Potential of Low-Cost Dust Monitors in Mining
By Ed Rutkowski
This morning at AIHA Connect 2024, NIOSH researcher Justin Patts presented the results of an ongoing project that explores the feasibility of using low-cost dust sensors in mines to monitor, and ultimately control, exposures to respirable crystalline silica. Patts’ presentation at the Greater Columbus Convention Center was timely given MSHA’s recent finalization of a standard that lowered its permissible exposure limit and action level for silica in mines to 50 µg/m3 and 25 µg/m3, respectively, as 8-hour time-weighted averages for full-shift exposures.
The research Patts summarized was part of a five-year project that began in 2019. As Patts explained, the project had three main goals: to characterize the performance of low-cost sensors in mines, build a smart filtration and pressurization system for mobile mine equipment, and quantify the effectiveness of these technologies.
Mining environments can change quickly, so constant monitoring is necessary to protect workers, a need that Patts summarized as “what you don’t know, you can’t fix.” While area and personal dust monitors have been around a long time, their high cost limits their adoption at mining sites. Area monitors can cost as much as $7,000 per unit, Patts said. Low-cost dust monitors are light-scattering instruments that operate by sensing the reflection of polarized light from particles. Their measurement accuracy is lower than that of area and personal monitors, but their small size provides greater accessibility.
Respirable particles are usually less than 10 microns in diameter, too small to be seen with the naked eye. These particles can travel deep into the lungs and cause adverse health effects, including silicosis, one of the world’s oldest occupational diseases. Historically, silicosis is associated with the Hawk’s Nest Tunnel disaster in West Virginia, which led to the deaths of more than 760 workers in the 1930s. More recently, concerns about silicosis among workers in the stone countertop industry have prompted efforts to ban engineered stone, which has a high percentage of crystalline silica content.
The first step in Patts’ project was to determine whether low-cost dust monitors could quantify the dusts at metal and nonmetal (MNM) mines. Over 15 days of testing in the lab, Patts’ research team assessed eight monitors against four types of dust and compared each instrument’s output against laboratory-grade equipment. The results showed a high degree of correlation.
Next, the team installed the low-cost dust monitors at four different MNM sites. These real-world environments resulted in occasional instrument failures, but once again, the testing was successful. The instruments’ output was highly correlated with that of gravimetric samplers.
Patts reminded his audience that the ultimate goal of the project was to use the instruments to make decisions about how to best protect workers through engineering controls. One challenge discovered during the project was the sheer size of the instruments’ output. “We found that the continuous accumulation of data by these sensors can start to get overwhelming pretty fast,” Patts said.
The research team worked with mine management at each location to figure out how to make the data usable for each workplace. One result was to transform the time-series data plots into calendar views, which allowed management to discern longer-term trends.
The low-cost dust monitors have been installed at the mines for a year now, and although there have been some failures, Patts said that the instruments are holding up well.
A second aspect of the project involves the installation of low-cost dust monitors in a “SmartCab,” which is a prototype for a ventilated enclosure intended to protect equipment operators from hazardous dust exposures. The prototype was tested last month in South Carolina, and the research team is still analyzing the data, Patts said.
The final step, Patts said, is to find a way to demonstrate the value of low-cost dust monitors to stakeholders. “It’s easier to justify the expenditure of engineering controls to your boss if you can tell him or her with certainty that it’s going to do what you said it’s going to do,” he explained. The team is still searching for the right project.
Ed Rutkowski is editor in chief of The Synergist.
Read more coverage of AIHA Connect 2024.