Summary of OSHA Combustible Dust Forum

On May 13, 2011, OSHA held an Expert Forum on Combustible Dust to discuss possible options for developing a comprehensive rule to address the hazards associated with combustible dust.  OSHA’s stated intent was to both protect employees and be cost-effective for employers. The major topics for discussion included: Scope; Focus on Preventing Secondary Explosions; Existing Facilities; and Multiple Layers of Protection. The meeting was divided into these four topics for discussion, and OSHA posed questions from each to the panel of experts. Below are the highlights from the meeting.


The term Scope, in the context of this discussion, refers to who and what the combustible dust rule will ultimately apply to.

  • The panel agreed that the rule should not specifically exclude any industry.
  • Some members of the panel suggested that dust with low explosive properties and hard-to-ignite dust should possibly be excluded, or at least should be addressed differently than more hazardous and easily ignitable dust.
  • Other members of the panel warned that there is no technical support for this exclusion, and pointed out a number of serious dust fire and explosion events that occurred due to what were thought to be “low-hazard” dusts. 
  • A member suggested that if any dust is to be excluded, it should only be a dust that is not combustible at all. 
  • Regardless, the panel agreed that if there was some type exclusion or limitation on which dust were covered by the standard, it should not be based on a single dust property.
  • One suggested test would be the ASTM test used to determine if a material can support propagation of a flame front.
  • The panel suggested that the size of a facility should not be a sole reason for exclusion. 
  • One possible exclusion from the rule could be based on quantity of dust at a facility.  One example is facilities with less than 5 lbs of aluminum dust.
  • A panel member suggested that size exclusions could apply to specific pieces of equipment, like in NFPA 654, but should not be based on facility size.
  • It was noted that the fatality rates in smaller facilities are actually higher than those in large facilities.

Focus on Preventing Secondary Explosions:

OSHA asked if focusing on preventing secondary explosions would be the best way to prevent multi-fatality events.  OSHA also asked if there would be a significant impact if the regulation omitted provisions to address primary explosions.

  • One panel member noted that 95-99% of fatalities and injuries are the result of secondary explosions that occur due to accumulated, fugitive dust.
  • The grain handling rule focused on housekeeping and ignition control, and that rule has been very effective.
  • The panel agreed that the first step is to keep dust inside the equipment and vessels, and not let it escape into the work environment.
  • One panel member stated that $1 spent to contain and/or capture the dust can save $10 in electrical classification, and save $100 in housekeeping cost over 10 years.
  • For dust that does escape into the work environment, it is important that safe housekeeping methods that cover all areas (including hidden, out-of-site areas) be conducted.
  • It was suggested that recordkeeping of housekeeping activities and inspection of hidden areas is important.
  • The panel stated that determining what level of dust accumulation presents a hazard is still being studied, and the rule should allow for advances in knowledge after it is developed. 
  • Most of the panel agreed that reducing the risk of secondary explosions is critical, but primary explosions can be very dangerous and cannot be neglected.
  • Housekeeping is an important part of controlling combustible dust hazards, but it is only part of a comprehensive management system needed. This system needs to include hazard recognition, engineering controls, employee training and involvement, maintenance and inspection, etc.
  • Some panel members suggested that some components of the Process Safety Management (PSM) rule, such as Hazard Analysis and Management of Change, could be beneficial, but most agreed that the full PSM regulation would not be appropriate.

Existing Facilities:

OSHA is concerned about the burden on employers if existing facilities must retroactively comply with the standards – particularly for higher-cost engineering controls.

  • A panel member stated that it is important to understand that the most severe incidents have occurred at “old” facilities, so grandfathering across the board would not address the greatest hazard.
  • However, several panel members did agree that in some cases, installing engineering controls at existing facilities is not feasible, either economically or technically.
  • One panel member noted that some controls mandated in NFPA standards are not always justified, and may be obtrusive.
  • It was suggested that if controls are required, that there should be a phased applicability so that employers do not have to make all modifications at once.
  • Several members emphasized the importance of conducting a hazard assessment, as the controls needed will be very facility specific and based on the actual hazards at each individual plant.
  • One possible method is to require facilities to conduct a risk assessment and develop their own priorities for installing controls.   
  • It was noted that NFPA standards have retroactively clauses, and typically only administrative controls (housekeeping, training, hazard analysis) and ignition source controls are retroactive.
  • Several panel members agreed that housekeeping, training, and ignition controls should be the first priority.
  • It was suggested that OSHA should include a list of high-hazard processes and equipment that an employer must evaluate (e.g. dust collectors, hammermills, spray dryers).
  • Also, it was suggested that the exposure to employees should be considered when prioritizing the protection needed.

 Multiple Layers of Protection:

OSHA noted that many fire and explosion control scenarios include multiple layers of protection, and asked if requiring only a single layer of protection (e.g. housekeeping) would be appropriate.

  •  The panel agreed that controlling dust fires and explosions require making a number of choices and selecting a number of controls.
  • Several panel members pointed out that each type of control has holes, and multiple layers are required to truly protect a facility.  For example, ignition controls are good, but it is impossible to remove all possible ignition sources.
  • It was noted that it is important to install multiple layers of controls in order to reduce risk to an acceptable level – though several members agreed that it is impossible to get to zero risk.
  • Therefore, it was agreed that it is necessary to evaluate each individual situation to determine what levels of control are needed.
  • It was a consensus that multiple layers of protection are needed, but one panel member urged that OSHA must include some flexibility in the rule, as not every hazard mitigation approach works for every situation – and there is no silver bullet for addressing combustible dust hazards.

My Personal Interpretation

 The expert forum provided OSHA with a number of points to consider.  I cannot predict exactly how OSHA will use the data, and I can’t say that what I walked out of the meeting with is the same that OSHA walke
d out with.  So, the following summary is only my opinion on how OSHA may, or should use the information provided in this expert forum.

  • The scope of the rule should cover all facilities that generate and handle combustible dust in a significant quantity. 
  • The rule should make preventing hazardous levels of fugitive dust accumulation a priority.  This should be achieved by proper engineering and maintenance of equipment and dust collectors, safe housekeeping, and training.
  • The rule should require some level of hazard / risk assessments.
  • Some engineering controls should be required retroactively, but there should be some elasticity in how facilities decide what controls are required.
  • The rule must contain multiple types of controls, both administrative and engineering, to be effective in reducing the hazards associated with combustible dust.