OSHA inspectors must consider a manufacturer’s or importer’s use of information gained from actual explosion events, lab testing, published data on similar materials or particle size to assure they have properly classified their products for combustible dust hazards under the revised Hazard Communication Standard (HCS), OSHA said in a recent guidance memorandum. 

The agency’s HCS was revised to bring it into harmony with a global standard. Since that standard does not contain a classification for combustible dust hazards, OSHA amended the standard's definition of “hazardous chemical” to include combustible dust so as to maintain coverage of the hazard under its HCS. 

That move has put the agency in conflict with industry stakeholders who claim inclusion of combustible dust in the new rule amounts to backdoor rulemaking. A lawsuit over the agency action is currently playing out in federal appeals court. 

Marc Freedman of the U.S. Chamber of Commerce said the memo perpetuates problems OSHA created by including combustible dust in the standard. He noted that the agency did not give stakeholders a full opportunity to comment on its inclusion of combustible dust during the HCS rulemaking. Freedman also complained that OSHA still does not have a definition of combustible dust, yet employers are expected to identify combustible dust hazards and train their employees about it. 

“The way the memo reads, it is effectively implementing a non-OSHA, consensus organization's definition without the benefit of rulemaking, without a feasibility analysis, economic analysis or examination of its effect on small business. That's not how it's supposed to be done,” Freedman said. 

In its memo, OSHA noted the HCS does not define combustible dust. OSHA explained that this omission results from ongoing OSHA rulemaking on the substance and efforts underway at the United Nations. Instead, the agency has provided interim guidance, including a definition in a national emphasis program (NEP). A number of voluntary consensus standards, most notably from the National Fire Protection Association (NFPA), also provide guidance, according to the agency. 

The HCS requires manufacturers and importers, called “classifiers” in the guidance memo, to “identify and consider the full range of available scientific literature and other evidence concerning the potential hazards” of their products in the form they are shipped and which might stem from normal use and foreseeable emergencies. There is no testing requirement. 

Actual experience following a deflagration or dust explosion often offers the best information about the product, OSHA said. In such cases, the product should be classified as a combustible dust unless it can be shown conditions surrounding the event are not expected to occur under normal conditions of use or in foreseeable emergencies. 

Absent that information, classifiers may rely upon reliable laboratory test data. The memo cites ASTM methods as well as an OSHA method found in its NEP. Another option is published test data, such as that distributed by NFPA and public databases, such as one from Germany called the “Gestis-Dust-EX” database. Data may be relied upon provided it derives from a material substantially similar to the classifier’s product, OSHA said. If laboratory data or positive published test data for similar substances are available but not used by the classifier, the inspector must ask why, according to the guidance.

Where no test data are available or testing is inconclusive, the classification may be based on available particle size, the agency said. If the material will burn and contains a sufficient concentration of particles that would pass through No. 40 or No. 35 sieves to create a fire or deflagration hazard, it should be classified as combustible dust.

The guidance was not meant to be all-inclusive, since other reliable methods may be available, according to the agency, encouraging its inspectors to consult agency resources in those instances. OSHA also pointed out that the guidance is not intended for downstream users. Rather it must be applied when inspecting manufacturers and importers, usually from referrals concerning inadequate or inappropriate labels or safety data sheets. Companies must comply with most provisions of the rule by June 2015.