Investigators Design Experimental Engineering Control for Silica Dust

NIOSH bag-assembly
NIOSH mini-baghouse assemblies installed on eight thief hatches atop a sand mover during filling operations. Photo courtesy of Mike Gressel and Jerry Kratzer, NIOSH.

Each year, millions of workers, primarily in construction, sandblasting, and mining, are at risk of silicosis (and lung cancer) from exposure to respirable silica dust RCS.

National Institute for Occupational Safety and Health (NIOSH) investigators study how to prevent workers’ exposure to this serious health risk.

Recently, they developed a novel engineering control, called the NIOSH mini-baghouse retrofit assembly, to help control RCS released from sand moving machinery on oil and gas extraction sites.

The NIOSH mini-baghouse consists of filter material and ductwork connected to a baseplate that clamps to the openings, called thief hatches, on top of a sand mover. The NIOSH mini-baghouse reduces sand dust emissions coming out of the thief hatches by trapping RCS before it disperses into the air where it would pose a health risk to workers.

The mini-baghouse was tested in the field at an Arkansas sand mine on November 18-21, 2013. During the trial, area air samples were collected at 12 locations on and around a sand mover with and without the NIOSH mini-baghouse control installed.

NIOSH results indicate that the NIOSH mini-baghouse effectively reduced both respirable dust and RCS downwind of the thief hatches. The reduction of airborne respirable dust ranged from 85% to 98%, and the reduction in airborne RCS ranged from 79% to 99%.

In another significant finding, a sample of dust collected by the mini-baghouse showed the presence of freshly fractured quartz, which is a particularly hazardous form of RCS.

Next steps are plans to enhance the performance of the NIOSH mini-baghouse with several engineering improvements to the clamping mechanism, filter fabrics, sealing surface, and material measurements.

After that, NIOSH plans to evaluate the new and improved NIOSH mini baghouse in the field and then commercialize and license the technology to industry.