Mining Project: Certification Test Protocol Development and Treated Rock Dust Deployment Strategies

Principal Investigator
Start Date 10/1/2015

To eliminate coal dust explosions in underground coal mines through the development of improved methodologies for identifying and mitigating explosible accumulations of coal dust.

Topic Area

Research Summary

30 CFR 75.402 mandates that underground coal mines are to be rock dusted in order to prevent coal dust explosion propagations. Current research by the NIOSH Mining Program has focused on the examination of each element of 30 CFR 75.2 (rock dust definition) and its relevance and applicability in the current mine environment. As a result, desired rock dust attributes such as the appropriate particle size, specific surface area, dispersibility requirements, percent incombustible content, and the maximum allowable silica concentration have been identified. However, there is no standard test protocol by which mine operators can certify the performance of rock dusts.

Current research has also identified a means by which rock dust can be treated to prevent caking when wetted and then dried. Caking adversely affects the dispersibility of the rock dust, rendering the rock dust ineffective to inert coal dust. The use of anti-caking additives can prevent rock dust from caking when exposed to water, but further research is needed to assess the deployment of treated rock dust and to evaluate its potential health effects. Since the treated rock dust is readily dispersible, the perception exists that it could contribute to the miners’ airborne respirable dust exposure levels. Therefore, there is a need to assess this potential concern through lab and in-mine studies.

To address this need, this project has eight research aims, as follows:

  1. Establish specific surface area relationships between rock dust and coal dust.
  2. Examine the application of anti-caking treated rock dust in coal mines and its impact (if any) on the airborne respirable dust concentrations.
  3. Evaluate the inerting effectiveness of anti-caking rock by conducting large-scale explosion testing.
  4. Reduce the generation of airborne respirable dust by developing foam/slurry rock dust.
  5. Quantify the silica content in various size fractions of the rock dust with particular emphasis given to the respirable size fraction.
  6. Examine the health effects (if any) of anti-caking treated rock dust through animal testing and toxicological studies.
  7. Provide laboratory test protocols for certification of rock dusts.
  8. Examine the possibility for eliminating ineffectual particles greater than 75 microns from the rock dust size distribution while maintaining inerting effectiveness. 

This project seeks test methods by which rock dust can be tested and certified as meeting the desired attributes to inert a propagating coal dust explosion. Another concern is that anti-caking rock dust will contribute to the potential respirable dust exposure upon re-entrainment by equipment and workers. Since treated rock dust is readily dispersible, it is imperative to determine if it contributes more to the airborne respirable dust concentrations in mines than untreated rock dust. Finally, this project also examines the possible health effects of both treated and untreated rock dust.

Page last reviewed: 3/17/2020 Page last updated: 10/28/2016