Tuesday, January 12, 2010

OSHA Ventilation Standard Revise for Combustible Dust

Reviewing the recent OSHA Combustible Dust NEP status report (Figure 6) illustrates that 90% of the citations for combustible dust arose from OSHA General Industry Standards. Approximately 10% of the citations were General Duty Clause citations where a majority of examples were for ventilation such as ductwork, dust collectors, and other aspects of the dust collection system used in ventilation. (pages 7-10 of 12 page .pdf)

The current OSHA General Industry Ventilation Standard 29 CFR 1910. 94 includes elements that address dust hazards in abrasive blasting, grinding, polishing, and buffing operations. Problem is, the Ventilation Standard originates more from an industrial hygiene viewpoint, where attention is directed towards respiratory hazards such as silica sand inhaled during blasting operations. What about combustible dust fire and explosion hazards from inadequate ventilation throughout the manufacturing sector?

Local Exhaust Ventilation
A key aspect in the fire triangle in reducing the possibility of a combustible dust fire or explosion is to remove the combustible dust fuel load. Good housekeeping alone will not completely remove the dust fuel load in most manufacturing processes, so dilution ventilation or local exhaust ventilation (LEV) must be utilized. Local exhaust ventilation (LEV) is the most effective in reducing explosive combustible dust concentrations.

Local exhaust ventilation (LEV) includes four major components: exhaust hood, ductwork, fan/ motor, and dust collector. The system must be properly designed and maintained so as to prevent and mitigate possible combustible dust related fires and explosions. Many of the combustible dust related fires occur or progress into the ventilation system. So it is extremely important that spark detection/flame suppression, abort gates, and explosion ventilation be incorporated in the industrial ventilation system.

General Industry Standards
The OSHA General Industry Ventilation Standard 1910.94(a)(2)(iii), does note that for abrasive blasting, the principles set forth in the National Fire Protection Association Explosion Venting Guide, NFPA 68-1954 be adhered to. What about other manufacturing processes where flammable or explosive dust mixtures may be present? There is a disconnect in many other General Industry Standards in not addressing combustible dust hazards such as in Hazard Communication, Housekeeping, and PPE. It's odd that Powered Industrial Trucks and Hazardous (Classified) Locations General Industry Standards address combustible dust, yet the majority of other General Industry Standards do not.

A proposed separate combustible dust standard does not address the antiquated OSHA General Industry Standards where many of the standards are from an industrial hygiene standpoint that fails to comprehensively address fire and explosion hazards concerning occupational safety. The Ventilation Standards in the maritime, construction, and general industry is an excellent example of this weakness.

For example, ventilation fire hazards in spray finishing are addressed in regards to solvent vapor there is the requirement 1910.94(c)(6)(ii) to dilute solvent vapor to at least 25 percent of the lower explosive limit of the solvent being sprayed. What about minimum explosive concentrations (MEC)/lower explosive limit (LEL) for combustible dust that is captured in the industrial ventilation system that are also possible fire and explosion hazards thoughout the manufacturing sector?

Potentially Explosive Atmosphere

Until OSHA recognizes that combustible dust is a potentially explosive atmosphere like in the above example for solvent vapors there will be a weakness in the Ventilation Standards that is mostly directed towards industrial hygiene. An excellent example where our international trading partners do understand that combustible dust poses an explosive atmosphere like flammable vapors, gases, and mists is the U.K DSEAR and EU ATEX Directives

OSHA cannot continue to address Industrial Ventilation as the
most important engineering controls solely from an industrial hygiene standpoint. Industrial safety is just as important and must be on the flip side of the coin. The OSHA Salt Lake Technical Center(SLTC), which edited the informative and educational OSHA Ventilation Health and Safety Topics page should know better. Especially when SLTC is conducting all the testing for combustible dust ignition sensitivity and explosion severity.

U.S. Bureau of Mines

Over two decades ago Martin Marietta Laboratories and Marcom Associates, Inc. under contract from the U.S. Bureau of Mines (USBM closed in 1995 and transferred to NIOSH in 1996), prepared an excellent 220 page document, "Dust Control Handbook For Mineral Processing." The educational content was mostly centered on respiratory hazards concerning industrial hygiene in the mineral processing industry.

Many of the excellent chapters are applicable to the design and maintenance of industrial ventilation so as to minimize combustible dust fire hazards. In addition to the resource being located on the OSHA Safety and Health Topic Silica, Crystalline pages it should be cross-referenced on the OSHA Safety and Health Topic Ventilation Additional Information page.


In conclusion from reviewing the OSHA Combustible Dust NEP status report it appears that too much emphasis is being directed toward the General Duty Clause. Especially when over 30 percent of the report provides examples of General Duty Clause combustible dust citations where a majority of these citations are for industrial ventilation issues. What the ComDust NEP status report failed to emphasize, was the 90% of citations arose from General Industry Standards. Powered Industrial Trucks was not even included in Figure 7 of the report. Many of these antiquated General Industry Standards have not come to terms with combustible dust fire and explosion hazards from an industrial safety standpoint.

A separate combustible dust standard will provide many with a warm and fuzzy feeling but does not address an alternative regulatory approach in revising the current General Industry Standards so as to comprehensively come to terms with the 21st century occupational safety fire and explosion hazards in the workplace.

Designing Dust Collection Systems by Gary Q. Johnson-Workplace Exposure Solutions


Anonymous said...

Perhaps the reason why 90% of the violations where for general industry standards in the OSHA Combustible Dust NEP is because of then Asst. Secretary Foulke's stated position that a seprate combustible dust standard wasn't necessary and the hazards being found by complinace officers could be covered under existing standards? In fact, a close reading of the Com Dust NEP directive instructs inspectors to do just that. Yet even with Foulke's stated position and the compliance advice provided in the directive, OSHA compliance officers still had to issue many GDC violations in order to address hazards where their standards failed them.

As Rich Fairfax has noted, the uptick in GDC violations as a result of the Combustible dust NEP is indeed "disturbing". When OSHA has to fall back on the GDC, it clearly shows that existing standards are not capable of preventing the hazards and the standard writers need to start scribbling. Looks like Solis, Michaels and Barb recognized this fact and so the process of vetting a new standard has begun.

The good news is the standard is being developed under the normal rulemaking process which demands industry participation rather than being adopted according to Congressional mandate where Congress and special lobbying interests would have crafred the language. Let's just hope OSHA can get the job done before we have another Imperial Sugar.

John Astad said...

Good review Anon. If you note the OSHA Combustible Dust NEP status report it includes inspection/citation data from October 2007 through June 2009. These dates include during and after the Asst. Secretary Foulke tenure.

Disturbing number of GDC violations? The majority of GDC violations were for industrial ventilation such as ductwork and dust collectors. Problem here, is is that 1910.94 Ventilation General Industry Standard was written mostly for occupational hygiene. What about fire and explosion hazards in regards to occupational safety?

A quick fix combustible dust standard as being debated does not address the antiquated General Industry Standards. So whats next a Vapor Cloud Explosion Standard, were there are many more fatalities and injuries from vapor cloud fires and explosions?

The OSHA standards were never developed to solely provide instructions for best engineering practices. A good example is the refinery industry which utilizes national consensus standards as reference for best engineering practices.

Currently the only reason that OSHA is developing a seperate standard is due to the CSB recommendations from the 2006 Dust Hazard Investigation. Not that all of sudden Solis, Michaels and Barb came up with the idea. Solutions in developing layers of protection is much more complex than the subjective recommendations that CSB provided. It is a great start, but much more complex in addressing solutions, which includes outreach, research, information, education, and training as the OSH Act mandated.

So special lobbying interests are not involved in the current OSHA rulemaking? Interesting.


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