If your facility manufactures, processes, blends, conveys, repackages, generates or handles combustible dusts, you will need a strategy. The purposes of this article will be for identifying, evaluating and controlling these combustible dust hazards. 

The best approach for developing that strategy is to perform a dust hazard analysis (DHA). In fact, the combustible dust safety standards issued by the National Fire Protection Association (NFPA) are mandating that you must conduct a DHA for your facility. Although the NFPA is not a government entity, federal and state governments recognize their standards as generally accepted good practices. The deadline for conducting a DHA for most facilities handling combustible dust was September 7, 2020. For agricultural and food facilities, the deadline has been extended to January 1, 2022. 

There are many different approaches for performing a DHA. NFPA 652 Standard on the Fundamentals of Combustible Dust presents general guidelines for the DHA and provides an example. Many additional references that describe various techniques and methodologies for DHAs are available including papers, presentations, webinars and books. Agricultural and food facilities may even be able to use the DHA checklist provided in Annex F of NFPA 61. A DHA will identify opportunities for improvement in safeguarding people, equipment and buildings from dust explosions and fires.  

The safety objectives here are very real. Dust explosions and fires can cause the loss of human life, create terrible burn injuries or destroy a business. Successful management of combustible dust hazards is important, but that does not mean that it is easy. Deciding what to do may be straightforward for some businesses. For a simple blending facility that handles one combustible dust, the number of DHA recommendations may seem quite manageable. Complex processing facilities with several combustible dusts, however, could be facing dozens, if not hundreds, of DHA recommendations. In these cases, many operators or owners may feel overwhelmed and left wondering where to begin. Are some of these recommendations more important than others? Does it make sense to implement each recommendation without modification, or should you consider alternatives? If a recommendation does not seem reasonable, do you still have to implement it?

In this article, we will provide some guidance on how to evaluate and prioritize your DHA recommendations. We discuss ways in which you can evaluate the merits of each recommendation, prioritize their implementation, monitor your progress and document the results.  

Dust Hazard Analysis Recommendations

According to the methodology described in NFPA 652, it is the duty of the DHA team to offer recommendations where they consider additional safeguards to be warranted. Depending on the size and complexity of the facility, this may result in a DHA that contains dozens of recommendations. Categories of recommendations may include equipment-specific housekeeping, ignition source control, documentation and/or management systems.  

It is common for a DHA to include a series of recommendations corresponding to apparent deviations from the approach prescribed within relevant NFPA standards. The NFPA 652 methodology, however, does not limit the types of recommendations that may be offered or provided. The DHA team considers them warranted, so the type and specificity of recommendations can vary widely. A prudent facility owner/operator has an obligation to evaluate and prioritize the DHA recommendations in a way that enables significant risk reduction in a timely, cost-effective manner. The facility, however, does not have an obligation to blindly accept all recommendations as written.  

Accept, Modify or Reject?

Facility owners/operators will find that the decisions related to combustible dust hazards are rarely a binary choice between implementing or not implementing a safeguard. In fact, further research often reveals multiple control and mitigation strategies available to comply with relevant NFPA standards, and in some cases, there may be acceptable alternatives not described in the standard. Some recommendations may require significant modification to be consistent with facility engineering requirements, internal standards, or to be compatible with other recommendations. As a result, some recommendations that seemed reasonable to the DHA team may not be possible or appropriate due to factors outside of its scope and purview. 

Consider, for example, a hypothetical recommendation to: “Add fugitive dust collector socks to weekly inspection checklist.” This recommendation may prove to be straightforward, or further analysis and discussion with operations may reveal that the dust collector cannot be safely opened outside of the annual plant turnaround. In the latter case, it may be determined that an annual inspection corresponding to the plant turnaround is adequate, or a different strategy, such as a different inline fan may be necessary to achieve the desired risk reduction. Alternatively, it may be determined that infrequent operation of the dust collector and the existing safeguards are adequate and that the recommendation may be rejected. 

To perform such an evaluation, it is often necessary to assemble a different or larger group of stakeholders, involving management and often subject matter experts. This group should be empowered to accept a recommendation as written (when appropriate), to modify the recommendation (when necessary) or to reject the recommendation (given proper justification to do so). Where a recommendation is accepted or modified, the group should assign the associated action items to individuals or groups. In any case, it is recommended that the decision be documented to provide future stakeholders a better understanding of the resolution process.  

Should You Manage Hazards or Risks?

Implicit to the consideration described above is a comparative evaluation of more than one approach to manage the same hazard, in other words, which actions will provide the “most bang for the buck.”

Even strict compliance with the NFPA standards can generally be achieved through multiple pathways and very rarely can the hazard be completely eliminated. A facility, therefore, must decide how to best manage these hazards. This is where risk enters the decision-making process. To understand risk, one must first define the terms hazard, consequence and likelihood: 

• A hazard is a source of potential harm. Combustible dusts may present fire and explosion hazards as they have the potential to participate in fires and explosions. 

• A consequence, in the context of these hazards, typically refers to a negative (or hazardous) outcome associated with a dust fire or explosion. These consequences may be financial, environmental, or health and safety related. 

• The likelihood of a consequence is an estimate of the frequency or probability that the consequence occurs. Likelihood may be expressed qualitatively or quantitatively. 

• The concept of risk combines the consequences associated with a hazard and the relative likelihood of those consequences becoming manifested. 

In the context of NFPA 652, risk can be defined as a measure that combines “the likelihood, vulnerability, and magnitude of the incidents that could result from exposure to hazards” (see for example the definition of Risk Assessment, Section 3.3.41). In other words, risk provides a common point of comparison between an unmanaged hazard and various hazard management strategies that incorporate a consideration of uncertainty. The process of evaluating risk is called a risk assessment. This process shares some of the same steps as a DHA, but a risk assessment employs risk as a measure to evaluate and compare hazard management solutions. 

Prioritizing Implementation for Risk Reduction

After recommendations have been considered and associated resolutions have been identified, it is often necessary to then prioritize implementation of recommendations. The DHA team may offer its own prioritization based on its understanding of the risk of hypothetical events that could be addressed by each recommendation and the extent to which risk reduction could be achieved by implementing each recommendation. 

Ultimately, facility management has the final say on how action items are prioritized and must determine which risks are the greatest risks and which recommendations achieve the greatest risk reduction. To effectively prioritize recommendation action items, facility management should define its risk management objectives, such as exposure to plant personnel or other people outside the facility, to equipment within the facility or to the stability of facility operations. These objectives provide a prioritization structure that may or may not be directly related to the prioritization offered by the DHA team. In some cases, there may not be enough information about potential accident scenarios to prioritize certain action items. A staged implementation could be used in this situation, where in some action items are prioritized and implemented while additional information is gathered for the outstanding action items.