2020 Rock Dust Partnership Meeting Questions and Answers

Questions asked by attendees at the Rock Dust Partnership meeting on September 30, 2020, and answers furnished by NIOSH staff.


This is my first invitation to this partnership which is great, and it is very interesting especially as I was at Master Builders Technology (now owned by BASF) when we provisionally patented and tested "foamed coal dust." Excuse my ignorance, but does this partnership form a part of a "holistic" project looking at training (poor practice leads to many explosions especially in China), electrical spark protection, lightning protection, spark reduction when cutting coal, and the final line of defense using water barriers? Sorry to ask perhaps a poor question but I am unaware of the history aside from the disaster about 11 year ago that correctly focused on this again.


Thank you for the question. We have initially concentrated on the science of preventing the explosions and filling the gap areas that the current rock dust definition has at the moment. That said, we have investigated other avenues and brought in the expertise of other groups when questions arise, such as the re-entrainment of rock dust (we received help from the Pittsburgh Mining Research Division respirable dust group) and the toxicity of anti-caking additives (HELD conducted studies for PMRD). Your suggestion of a holistic review is good, and we will consider it. A publication incorporating these views may be appropriate.


Further to our brief exchange at the Rock Dust Partnership Meeting, […] I didn't mean to imply that NIOSH would fund this side of it but NMA or an equivalent body may be interested in it for the education of industry related training and to offer the public a unique and safe mining experience.


Thanks for the clarification. As you may know, the NIOSH Pittsburgh Mining Research Division operates two underground research mines on the Bruceton campus – the Safety Research Coal Mine (SRCM) and the Bruceton Experimental Mine (BEM), in addition to a number of world-class laboratory test facilities. We have on many occasions hosted industry, labor, and government-related groups, in addition to faculty and undergraduate and graduate students from various mining departments. They have used our facilities and collaborated with our technical staff to support their on-going education and research efforts. Your point to explore education-based uses for the future Mace property is well-taken. As we move forward with development of the Mace property, this topic will undoubtedly come up; as our organization has a long history of such collaborations. I would welcome continuing our conversation in the future.


What is NIOSH and/or MSHA's current guidance for suppliers in meeting the dispersion requirement prior to a finalized, standardized test procedure?


NIOSH would have to defer to MSHA and 30 CFR 75.2 on this. However, NIOSH has the following publications for guidance in which dispersibility of rock dust has been explored:

Brown, Connor B; Perera, Eranda; Harris, Marcia L; Chasko, Linda L; Addis, James D [2020]. Laboratory development and pilot-scale deployment of a two-part foamed rock dust. 13th International Symposium on Hazards, Prevention, and Mitigation of Industrial Explosions, Braunschweig, GERMANY – July 27-31, 2020

Perera IE, Harris ML, Sapko MJ [2019]. Examination of classified rock dust (treated and untreated) performance in a 20-L explosion chamber, Journal of Loss Prevention in the Process Industries 2019 Nov; 62:103943

Sapko, M.J., Harris, M.L., Perera, I.E., Zlochower, I.A., Weiss, E.S. [2019]. Factors Affecting the Performance of Trickle Dusters for Preventing Explosive Dust Accumulations in Return Airways. Journal of Loss Prevention in the Process Industries (2019).

Brown CB, Harris ML, Perera IE, and Sapko MJ [2018]. Laboratory Assessment of Various Rock Dust Foams. In: Proceedings of the 12th International Symposium for the Hazard, Prevention, and Mitigation of Industrial Explosions, Kansas City, MO, August 12-17, 2018. 7 pp.

Isaac A. Zlochower, Michael J. Sapko, Inoka E. Perera, Connor B. Brown, Marcia L. Harris, and Naseem S. Rayyan [2018]. Influence of Specific Surface Area on Coal Dust Explosibility Using the 20-L Chamber. Journal of Loss Prevention in the Process Industries, 54, 103-109.

Perera IE, Harris ML, Sapko MJ, and IA Zlochower [2017]. A Characterization of Classified Rock Dust - Examining Inerting Efficiencies and Wicking Properties. 16th Mine Ventilation Symposium, Golden, Colorado, June 17-22, 2017.

Harris ML, Organiscak J, Klima S, and IE Perera [2017]. Respirable Dust Measured Downwind during Rock Dust Application. Mining Engineering, Vol. 69, No. 5, pp. 69-74.

Perera IE, Sapko MJ, Harris ML, Zlochower IA, Weiss ES [2016]. Design and Development of a Dust Dispersion Chamber to Quantify the Dispersibility of Rock Dust. Journal of Loss Prevention in the Process Industries, Vol. 39, pp 7-16, January 2016.

Harris ML, Sapko MJ, Zlochower IA, Perera IE, Weiss ES [2015]. Particle Size and Surface Area Effects on Explosibility Using a 20-L Chamber. Journal of Loss Prevention in the Process Industries, Vol. 37, pp 33-38, September 2015.


Question about the foam. Can you clarify for me if the foam works the same wet vs. dried? If not, time needed to dry and how will a wet, humid conditions impact the ability for the foam to dry? Thanks.


We do not have experimental data to answer your question “if the foam works the same wet versus dried?” There are reasons to believe, based on previous independent tests with low expansion aqueous (firefighting) foams, that the initial pressure front impacts the foam, fractures the foam cells and then forms a micro-mist of gaseous suspension of very fine water droplets, vaporizing and rapidly extracting ~970 BTU/lb, and cools the combustion front. The large latent heat of vaporization of water is what makes water mists more effective than rock dust particles in quenching explosions.

Page last reviewed: January 7, 2022
Page last updated: November 3, 2020