Analyzing Your Dust Hazards

To be compliant with OSHA's general duty clause for workplace safety, facilities that produce potentially combustible dust should do everything they can to ensure compliance with NFPA 652.

• By Tim Colliton
• Jul 01, 2017

The National Fire Protection Association was founded in 1896, and for the past 120 years the trade association has created and maintained fire protection and safety standards and codes for adoption and usage by city, county, and state governments across the country. One such code that is critical for manufacturers to be aware of is NFPA 652, which governs combustible dust standards and practices in facilities. Any facility that processes or handles combustible solids or dust such as foodstuffs, wood, plastics, and metals must take careful steps to identify and manage the potential fire and explosion hazards lurking in its everyday operations.

You don't have to look far to find tragic examples of the consequences of not identifying and mitigating fire and explosion risks related to suspended fine dust particles in manufacturing operations. Perhaps the most notable example is the February 2008 explosion at the Imperial Sugar factory in Port Wentworth, Ga.—a disaster that took the lives of 13 people and injured as many as 40.

The worst part about these types of industrial disasters is that they are entirely preventable. To get at this problem, NFPA 652 requires that facilities with combustible dust potential be evaluated for combustible dust hazards no later than September 2018.

NFPA 652 is an example of a "consensus standard," meaning that most jurisdictions don't have it codified into law but it is the consensus of experts that the standard should be complied with. These types of standards often become law over time as state legislatures or even county and city governments update their laws and codes. At the federal level, OSHA has proposed a new standard related to combustible or explosible dust, but new federal regulation is likely some time away. However, to be compliant with OSHA's general duty clause for workplace safety, facilities that produce potentially combustible dust should do everything they can to ensure compliance with NFPA 652 in the meantime.

And it isn't just brand-new facilities that need to worry about meeting the standard. There are certain aspects and requirements of NFPA 652 that are retroactive to existing facilities that were in existence or substantially complete on the date the standard was published, which was Sept. 7, 2015.

Preparing for a Dust Hazard Evaluation--Conducting a Walkthrough
So, with the deadline looming, what should these types of facilities expect when it comes to an evaluation? How can they prepare? And what should they do once their findings are known?

The first step in getting ready is to conduct a thorough walkthrough of your facility and your processes to identify potential dust hazards. Items that facilities need to start paying attention to generally fall into three categories: housekeeping to control dust accumulations; ignition source control, which is limiting hot surfaces, static electricity, and other spark producing devices; and management programs, which involve reviewing and evaluating workplace management controls, such as prohibiting hot work or other actions that could provide an ignition source.

With so many factors to consider within your building and operations, it can be overwhelming to even know where to start. Wisely, that is why the standard also requires a dust hazard evaluation.

However, you don't have to wait for a formal dust hazard evaluation to identify problems and begin to make changes. In many cases, facilities may know they have issues they need to address and they'd prefer to tackle the low-hanging fruit before having an evaluation. In that case, a qualified consultant can do a walkthrough of your facility and your manufacturing processes and help you identify hazards. These walkthroughs are fact-finding expeditions in which the risks are identified and prioritized to give the facility management team a punch list of needed improvements that will likely come up on an evaluation.

A consultant can also help you identify steps within your processes that may create a hazard. For instance, in any process that handles combustible dust or other potentially combustible materials, the form and composition of the materials may change throughout the process. What may not have been combustible in steps one to 101 may become combustible in the next manufacturing step due to changes in material composition or the introduction of a new element. You must understand exactly what is happening at each stage of your process to understand where the real issues are.

Dust Sampling and Laboratory Testing
A consultant will help develop a comprehensive sampling plan to take dust samples at numerous locations around your facility, as well as at each potentially hazardous process step identified during the walkthrough. These samples will then be laboratory tested to determine their level of combustibility. Lab testing will determine whether your dust can be ignited under a wide variety of circumstances and will give you the data you need to either prevent it or mitigate it.

Facilities working without an experienced consultant also can implement testing if they develop a sampling plan that covers the basics and they have a person on staff who is familiar with the characteristics of combustibility of dust and how the steps of their manufacturing process impact those characteristics. Facilities doing testing themselves can usually locate contract laboratories that will test their samples and give them a report to document the findings.

The initial laboratory testing is a basic "go/no go" style test that determines whether the dust will combust under a variety of conditions. These tests typically run around $1,000 to complete, and results are usually relatively quick. If your dust is noncombustible, you are good to go. If it does combust under testing, then a battery of additional testing is needed to determine at what minimum concentration can be ignited, what is the minimum amount of ignition energy required to create an explosion, and other parameters. These tests can run about $5,000 to complete.

Conducting a Dust Hazard Analysis
The dust hazard evaluation is the step that helps things come together for most facilities. It helps management teams to answer key questions and understand the size and scope of their potential dust hazard, as well as the circumstances that contribute to the danger level, in order to develop the management systems needed to mitigate risks and prevent continued problems.

A dust hazard analysis usually includes a table exercise with the key personnel there who know the building equipment and processes involved. This may include an outside consultant as a facilitator but also may include production managers, plant engineers, maintenance engineers, quality control inspectors, and even material handlers. Depending upon your facilities’ products and processes, you may have specialized staff such as a plant chemist who should be a part of the analysis.

Once the team is assembled, the group will go through the entire manufacturing process step by step and identify all of the aspects of that step that could contribute to a hazardous condition. For instance, if 50-pound bags of material are poured into a machine hopper, what happens if too much or too little material is added? If the temperature control on that machine fails, could an ignition source be created? What if some other control system fails? Could a ventilation system be added to collect and remove dust associated with dumping these bags? Or could the materials be loaded in different increments, or via a different method, to eliminate the dust? The team collectively brainstorms the potential problems that could pop up at each step, to be able to plan for contingencies to mitigate potential disaster.

When no problems are found, the team moves to the next step. If a potential problem is uncovered, the team brainstorms how to fix that problem to prevent its occurrence. When possible, engineering solutions are created to eliminate potential problems and prevent human error. When engineering solutions are not feasible, management solutions are implemented to control human behavior.

Once the team has gone through the full process and has identified the risk points, as well as the degree of risk, it can then prioritize the response and begin to implement mitigation options.

Revisiting Dust Hazard Analysis Over Time
No process is stagnant for its lifetime. There will be times when you choose to upgrade equipment, modify your manufacturing process, or expand your operations. Each significant change is another opportunity to evaluate and stop to ask yourself, "Okay, what's the impact of doing this? Are we causing more hazards? If so, how are we going to deal with those?"

Eliminating dust hazards comes down to vigilant awareness of your facility and your practices and an understanding of what creates an unsafe condition.

Consultants are available to help you through the process of getting ready for, and conducting, a dust hazard analysis. Whether you choose to use a consultant or go it on your own, keep in mind the basics of good dust handling practices, be thorough in your planning and prep work, and follow through on mitigating any risks that are identified. As past industrial disasters have shown us, the cost of doing nothing is far too high to ignore.

This article originally appeared in the July 2017 issue of Occupational Health & Safety.