A caution sign warning of a danger caused by a malfunctioning Baghouse

Bay Minette, Alabama – A Baghouse fire at a furniture manufacturing plant led to the closure of the entire site for several days. The Bay Minette, Alabama plant operated by Standard Furniture Manufacturing Co. suffered an explosion and ensuing fire in two silos that contain sawdust collected by the plant’s larger dust collection system.

While the exact cause of the explosion, and subsequent fire are not yet known, it is expected that an ignition source (such as a spark or an electric arc) may have been caused during a maintenance procedure.

The 600+ employees of the plant had to remain at home until the Baghouse was repaired and back in operation. This was further delayed when fire inspectors from the local fire department requested that the Baghouse be taken apart to aid them in their investigation of the fire.

This incident, one of many that occur each year, illustrates the importance of a site’s Baghouse, and larger dust collection system to maintaining normal operations. These often overlooked systems can when they malfunction due to maintenance neglect, improper operation, poor design, or other reasons lead to immense immediate costs for plant operators, and even larger long term ones.

Therefore this example highlights the need for constant attention to be given to dust collection systems so as to avoid these expenses, and therefore reduce overall operating costs. Only by maintaining a program of regular Baghouse maintenance, providing operators with sufficient training, ensuring all systems are adequately sized for the facility’s needs and meet all safety standards, can costly incidents like this one be avoided.


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Aftermath of a dust explosion at the Imperial Sugar Plant

Dominick DalSanto
Environmental & Dust Collection Technologies Expert & Author

On February 7th 2009 an explosion at the Imperial Sugar Refinery in Port Wentworth, Georgia kill 14 workers, injured dozens more, and resulted in millions of dollars worth of damages. What was the source of this horrifically powerful industrial explosion that took over a dozen lives and completely destroyed an entire factory? Was it some exotic chemical substance that was being used as part of some industrial process?

This devastating explosion was fueled by nothing other than a simple accumulation of otherwise harmless sugar dust.

In an industrial setting otherwise benign substances such as flour, corn, sugar, metals, or wood, can accumulate. When exposed to an ignition source these can lead to immensely powerful explosions.

Bowing to concerns over a lack of standardize federal safety regulations in this area, members of the U.S. Congress have recently taken steps to combat this danger.

Congress Attempts to Force OSHA’s Hand in Setting Combustible Dust Standards

Photo of the U.S. Capital building. Where the U.S. Congress is looking to pass legislation to force OSHA to set a comprehensive combustible dust standards and safety regulations


With such a large amount of deaths, injuries, and property damage being caused each year by combustible dust related fires and explosions, lawmakers are looking to draft legislation to provide safety standards for operations where the danger of combustible dusts exists

Recently three members of the U.S. Congress, Rep. George Miller (D-CA), Rep. John Barrow (D-GA), and Rep. Lynn Woolsey (D-CA), reintroduced legislation  concerning combustible industrial dusts. The Worker Protection Against Combustible Dust Explosions and Fires Act, would force OSHA (Occupational Safety and Health Administration) to set definitive standard

s regarding hazardous levels of combustible dust like coal, sugar, or metals dust in industry. This will accelerate efforts that are already in motion by OSHA. However the forthcoming OSHA standards are expected to take at least 4 years before codification and total implementation takes place.

Rep. Miller, who is a leading member of the House Committee on Education and the Workforce, commented that although he commends OSHA for beginning to take the initial steps to address this hazard, he feels that because of bureaucratic “red tape”, workers that are exposed to these hazards will not be fully protected for years. “While some industries have taken steps to address these hazards, workers are still being killed and injured from preventable combustible dust explosions. Regulatory delays should never be an excuse not to protect workers from a preventable tragedy” stated Miller.

CSB Makes Recommendations, But Finds no Comprehensive OSHA Standards for Combustible Dust

The governmental agency charged with investigating industrial incidents of this kind is the Chemical Safety Board. The CSB while charged with investigating industrial incidents, does not have the authority to issue regulations. Instead the agency merely issues reports details the causes of any particular incident, and then makes recommendations on how to avoid having a repeat incident.

Following a series of dust explosions, in 2006 the CSB undertook a thorough study of combustible dust hazards in industry. The CSB found that despite being a well-known industry hazard, there was no comprehensive set OSHA standards covering combustible dust hazards. In view of the immense danger to live and property that combustible dust hazards pose, the CSB recommended that OSHA begin work immediately to issue a comprehensive set of standards in this area.

In an industrial setting, dust can accumulate on areas such as floors near dust sources, and elevated spaces such as ceiling rafters/trusses, on the tops of machinery and shelving. Even accumulations of less than one inch can pose a great danger. Often times an initial explosion or fire  can take place which is quite small and localized, such as within a dust collector or related ductwork. However the resulting shockwave, even though it might be relatively small can then disperse or aerosolize larger deposits of accumulated dust which then will fuel a much larger secondary explosion, which can then propagate throughout the entire facility, causing massive destruction of property, and loss of life.

Between 1980 and 2005 combustible dust explosions killed at least 119 people, injured 718 and resulted in millions of dollars in damage in the U.S. alone. In the UK government statistics show that on average one death per week is caused by combustible dust explosions.

Dust Combustible Dust Safety Standards, Why So long in the Making?

With decades of documented cases of violent conflagrations caused by accumulation of combustible dusts, many are asking ask why has OSHA been so slow in issuing safety standards? No doubt a mixture of bureaucratic red tape, preoccupation with other so called “more pressing matters” and a general sense of complacency have all contributed.

However those affected by these terrible accidents want to see that others are not at risk to suffer the same way they have. “We know that standards OSHA has established in other areas have saved thousands of lives,” says Woolsey. “Workers need a standard on combustible dust, and they need it now.” Rep. Barrow added “This legislation will finally provide our nation’s factory workers with the protections they deserve.”

It appears now however that due in part increased activism, combustible dust hazards are being brought to the forefront of industrial safety as well as public attention. * See CBS 60 Minutes Highlights The Dangers of Dust Explosions

Now with new legislation being put forth, and at least partial self-regulating on the part of industry, it seems that progress is being made to give the needed attention to this serious industrial hazard.



What Can Be Done Now to Avoid Dust Explosions?

Explosions caused by combustible dust, are most often the result of neglecting to recognizing the dangers involved with combustible dust. Being aware of the danger accumulated dust poses is the first step in preventing a violent conflagration from taking place.

In general, there a few keys to safeguarding a plant from these dangers:

Good house-keeping practices throughout the facility – This would including cleaning up any large accumulations of dust, especially accumulations on elevated sites such as ceiling trusses or rafters, on top of storage shelving, and machinery.

Employing a dust collection system – The dust collector or Baghouse, will need to be sufficiently sized to handle the dust loads of the facility. Additionally, the correct type of Baghouse, Baghouse filters, and cleaning mechanism are all vital to ensure adequate collection operation throughout the entire facility. Ductwork design, and installation also play a vital role in ensuring that there are a sufficient amount of collection points throughout the facility in all dust producing areas. Also even the best dust collection system will be worthless if it is operated improperly, or left in a state disrepair due to in adequate maintenance.

Adequate knowledge of dust characteristics – It is vital that each kind of dust present be identified and their individual characteristics be understood. Many companies exist that will perform testing to determine the combustibility and other characteristics of any compound produced at a given site. This information is required to formulate a comprehensive dust control plan for the facility. This information also comes into play when selecting an appropriate dust collector system, filters, and installation and implementation.

Further more extensive information on how to prevent dust explosions can be found here on in the article: The Potential for Dust Explosions in Dust Collection Systems.


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A new report by leading industry experts states that 2000 dust explosions in factories and industrial facilities across Europe each year. An average of 50 per year are reported in the UK alone, nearly one a week. The report prepared by Dr. Julian Hought of risk management specialists, HFL Risk Services, also highlights that a large percentage of these incedents do not involve what we would normally classify as high-risk manufacturing processes, such as chemical production. In fact nearly 24% of incidents reported occurred in the food industry, with products as benign as flour, coffee, and sugar.

The report however stresses that a large part of the problem is that companies and employees do not realize just how dangerous these dusts can be when found in hazardous amounts within facilities. Proper dust collection equipment, and employee hazardous dust safety training are key to preventing these often deadly accidents from taking place.

To read the full report, please click here:


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Dust Explosion at the Imperial Sugar plant in Georgia

By Dominick DalSanto
Environmental Expert & Author

The dangers of combustible dust explosions are among the most overlooked of industrial workplace safety issues. However the price for negligence in this area is often payed not only with millions of dollars, but with workers very lives.

But only recently has the this issue began to attract mainstream attention outside of the industrial world. Recent incidents such as the one that occurred at the Imperial Sugar Plant in Port Wentworth, Georgia on February 8th 2007 that claimed the lives of 14 works, and injured 38 others, have brought this safety issue to the forefront of industrial safety activists.

This segment from the CBS new program “60 Minutes” entitled: The Danger of Combustible Dust – examines the efforts of the victims families and others to force OSHA to create a national combustible dust standard.  Scott Pelley reports on the deaths and property damage caused by dust explosions at American factories, a problem critics say the government needs to do more to prevent.

This report which is of great interest to all in the dust collection industry can be viewed at the link below.;photovideo

About the Author


At least 281 combustible dust fires and explosions occurred in general industry between 1980 and 2005 in the United States, which caused at least 119 fatalities and 718 injuries; including seven catastrophic dust explosions in the past decade, involving multiple fatalities and significant community economic impact; and occurred in a wide range of industries and involved many types of combustible dusts.

According to a report by the US Chemical Safety Board (CSB) a major factor that lead to the high amount of incidents was the overall lack of education regarding the danger of Dust Explosions. Without this information, plant operators are not able to implement proper safety precautions, and adequately train their personal about the precautions they need to take to minimize the chance of a Dust Explosion occurring in their facility.  This article has been prepared to help bring awareness to the dangers of Dust Explosions, and what precautions can be taken to avoid them.

What Is A Dust Explosion?

A factory that has been destroyed by a Dust Explosion

A Dust Explosion that begins in the Dust Collection System can lead to the destruction of an entire facility.

Most solid organic materials, in addition to many metals and inorganic nonmetallic materials, when reduced to a finely divided size, and sufficiently dispersed into the atmosphere will explode under the right conditions. Many combustible dusts are intentionally manufactured for a wide range of applications such as Metallic Powder Coatings, or certain foodstuffs such as Corn Starch, Flour, and Granulated Sugar. Others are produced during the manufacture and transport of materials such as wood processing, and stone quarrying. Additionally, during the manufacturing process for many materials, actions such as milling, polishing, and transportation may create substantial amounts of dust that can later accumulate on a wide range of surfaces.

Any industry that produces materials of a fine particle size that are combustible, and many that simply though their day-to-day operation create large amounts of secondary dust are at risk for Dust Explosions. Industries such as Metal, Food, Plastic, and Wood Processing are just a few that are at risk for this kind of industrial accident.

The Anatomy of a Dust Explosion

The Beginnings

The basics of combustion deal with the so called “Fire Triangle” that illustrates the importance of the three main factors that need to be present for combustion to take place. These three are Fire, Heat (Ignition Source) and Oxygen. With regards to Dust Explosions, we need to add another two ingredients to create what has been termed the “Dust Explosion Pentagon” Dispersion and Confinement. When all five of these factors are present in the right balance, a dust explosion will occur. The more of these factors that can be controlled or be kept below the combustion threshold, the less likely there will be an incident.

When a material is finely divided into a dust or power form it in most cases it becomes much more likely to combust than it would in a solid state. The reason for this is because when a material is smaller in size, and is dispersed into the air, it creates a much larger surface area to ignite. For example, a 1 kg sphere of a material with a density of 1g/cm3 would be about 27 cm across and have a surface area of 0.3 m3. However, if it was broken up into spherical dust particles 50µm in diameter (about the size of flour particles) it would have a surface area of 60 m² This greatly increased surface area allows the material to burn much faster, and the extremely small mass of each particle allows it to catch on fire with much less energy than the bulk material, as there is no heat loss to conduction within the material.

The source of ignition in a Dust Explosion is often times very difficult if not impossible to determine with absolute certainty. This is because in an industrial setting there is such a larger amount of possible ignition sources that after an incident, it cannot always be pinpointed with absolute certainty.  Some possible sources include, Open Flames, Electrostatic Discharge, Friction, Chemical Reactions, Arcing (From machinery or other equipment) and Hot Surfaces.

Primary and Secondary Explosions

Primary Dust Explosions, in an industrial setting, usually involve a dust cloud (Dispersed Dust) that is ignited by an ignition source. This explosion while possibly involving a substantial amount of dust is often not the most devastating. That is because this initial explosion can cause a pressure wave that can dislodge settled dust from other areas within a facility (Such as on the top of structural elements like beams and columns, high shelving, and machinery, or other areas that dust and debris may collect) causing it to disperse and then cause a much larger explosion that is termed a Secondary Dust Explosion. The majority of fatalities, and damage caused by dust explosion incidents, are actually caused by Secondary Dust Explosions.

Conditions That Lead To A Dust Explosion

The same CSB report cited earlier, after having discussed several different Industrial Dust Explosion Incidents, concluded that while all had many different factors that contributed to the respective incidents, all had the following circumstances in common:

* Facility management failed to conform to NFPA (National Fire Protection Agency) standards that would have prevented or reduced the effects of the explosions.
* Company personnel, government standards enforcement officials, insurance underwriters, and health and safety professionals inspecting the facilities failed to identify dust explosion hazards or recommend protective measures.
* The facilities contained unsafe accumulations of combustible dust and housekeeping to remove such accumulations was inadequate.
* Workers and managers were often unaware of dust explosion hazards.
* Procedures and training to eliminate or control combustible dust hazards were inadequate.
* Previous fires and other warning events were accepted as normal, and their causes were not identified and resolved.
* Dust collectors were inadequately designed or maintained to minimize explosions.
* Process changes were made without adequately reviewing them for potential hazards.

Listed here are a few of the summery reports published by the CSB. As you will see the above-mentioned factors all played a role in the eventual incidents.


In February 1999, a deadly fire and explosion occurred in a foundry in Massachusetts. The Occupational Safety Health Administration (OSHA) and state and local officials conducted a joint investigation of this incident. The joint investigation report1 indicated that a fire initiated in a shell molding machine from an unknown source and then extended into the ventilation system ducts by feeding on heavy deposits of phenol formaldehyde resin dust. A small primary deflagration occurred within the ductwork, dislodging dust that had settled on the exterior of the ducts. The ensuing dust cloud provided fuel for a secondary explosion, which was powerful enough to lift the roof and cause wall failures. Causal factors listed in the joint investigation report included inadequacies in the following areas:

* Housekeeping to control dust accumulations;
* Ventilation system design;
* Maintenance of ovens; and,
* Equipment safety devices.


In January 2003, devastating fires and explosions destroyed a North Carolina pharmaceutical plant that manufactured rubber drug-delivery components. Six employees were killed and 38 people, including two firefighters, were injured. The U.S. Chemical Safety and Hazard Investigation Board (CSB), an independent Federal agency charged with investigating chemical incidents, issued a final report2 concluding that an accumulation of a combustible polyethylene dust above the suspended ceilings fueled the explosion. The CSB was unable to determine what ignited the initial fire or how the dust was dispersed to create the explosive cloud in the hidden ceiling space. The explosion severely damaged the plant and caused minor damage to nearby businesses, a home, and a school. The causes of the incident cited by CSB included inadequacies in:

* Hazard assessment;
* Hazard communication; and
* Engineering management.



In February 2003, a Kentucky acoustics insulation manufacturing plant was the site of another fatal dust explosion. The CSB also investigated this incident. Their report3 cited the likely ignition scenario as a small fire extending from an unattended oven, which ignited a dust cloud created by nearby line cleaning. This was followed by a deadly cascade of dust explosions throughout the plant. The CSB identified several causes of ineffective dust control and explosion prevention/mitigation involving inadequacies in:

* Hazard assessment;
* Hazard communication;
* Maintenance procedures;
* Building design; and,
* Investigation of previous fires.


Finely dispersed airborne metallic dust can also be explosive when confined in a vessel or building. In October 2003, an Indiana plant where auto wheels were machined experienced an incident, which was also investigated by the CSB. A report has not yet been issued, however, a CSB news release told a story similar to the previously discussed organic dust incidents: aluminum dust was involved in a primary explosion near a chip melting furnace, followed by a secondary blast in dust collection equipment.

Prevention, Safety and Mitigation

Now that we have discussed many of the contributing factors that can lead to a Dust Explosion, we are going to highlight several areas that if given the proper attention, will lead to a safer working environment, and lessen the potential for property damage bodily harm.

Hazard Analysis

We have discussed the great danger that Dust Explosions can pose to life and property. Now we have listed several areas that if given the proper attention will greatly reduce the probability of a dust explosion occurring, and should one occur, lessen the severity of said explosion, possibly saving lives and lessening the damage to the facility in the process.

Facility Dust Hazard Assessment

Being aware that the possibility of a Dust Explosion exists is the first step to avoiding one. As mentioned previously, most dusts or powders will burn and if dispersed in the air in the right proportions and may explode. The same CSB study quoted earlier found that despite the long history of Dust Explosions in industry, in many cases the hazards involved with explosive dusts were largely ignored by plant operators, as well as by outside insurance auditors and government inspectors. Therefore, recognizing the great potential for this kind of accident during the initial design of the facility and while doing regular hazard analysis, are crucial

Here are some of the items to look for when conducting a facility hazard analysis with regard to the potential for Dust Explosions.

Dust Combustibility

Above all else, it must be determined whether or not that various types of dust produced in the facility are indeed combustible. As stated before, most materials in dust or powder form will burn when dispersed into the air in the right proportions. However, those proportions vary with each material. Therefore, it is vital for those responsible to gather as much data as possible about the particular materials present in the facility. One potential source of said data is the particular material’s MSDS or Material Safety Data Sheet. In some cases, additional information such as combustibility test results will be available from chemical manufacturers. However as noted before, many times a manufacturer MSDS may be lacking sufficient data regarding the combustibility of the material in dust or powder form. Therefore additional testing may be necessary to determine this information.

Electrical Considerations

Areas that require a special electrical equipment classification due to the presence (or potential presence) of dubitable dust need to be identified during a facility hazard analysis. There are several published sources of guidelines and/or regulations regarding special electrical equipment classification. These include: The OSHA Electrical standard (29 CFR Part 1910
Subpart S), NFPA 70, the National Electrical Code®, and NFPA 499, Recommended Practice for the Classification of Combustible Dusts and of Hazardous (classified) Locations for Electrical Installations in Chemical Process Areas.

Several of these guidelines identify three different groups of combustible dusts, (Metal, Carbonaceous and Other) and the different safety considerations that are needed for each. For example Metal dusts are considered electrically conductive; therefore special care needs to be taken to ensure that no electrical current can pass through layers of the dusts causing short circuits and arcs, which could then lead to an ignition. Additionally, in certain industrial settings, other high-energy ignition sources such as welding arcs may be present and need to be accounted for.

Potential For Dust Accumulation

The exact amount of dust accumulation necessary for an explosion to occur can vary greatly. As discussed earlier variables such as particle size, methods of dispersion, ventilation system models, air currents, physical barriers and volume of the area where the airborne dust exists can all vary in each different type of dust. With the site-specific data at hand, potential areas of concern can be identified. And the hazard analysis can then be tailored to the specific circumstances in each area and the full range of variables affecting the hazard.

Even seemingly small amounts of accumulated dust can cause catastrophic damage. The CSB estimated, for example, that the explosion that devastated a pharmaceutical plant in 2003 and killed six employees was caused by dust accumulations mainly under 0.25 inches deep. The NFPA warns that more than 1/32 of an inch of dust over 5 percent of a room’s surface area presents a significant explosion hazard.

Many different locations throughout a facility can be a potential starting point for a conflagration. An area where dust is concentrated is an obvious place to start. In Dust Collectors for example, a combustible mixture of diffused dust and air can be found whenever the Collector is operating. Additionally, locations where dust can settle whether occupied, or concealed spaces (such as in ceiling rafters, the tops of shelving, etc). When conducting the Hazard Analysis, careful consideration needs to be given to all possible scenarios in which any previously identified settle dust can be dispersed into the air, either though normal operations, or potential failure modes.

Precautionary Measures

After hazards have been assessed and hazardous locations are identified, one or more of the following prevention, protection and/or mitigation methods may be applied.

Dust Control

Controlling the amount of dust generated, where it is generated, and the dispersion of it throughout the facility, is key to reducing the likelihood of an explosion from occurring. The following steps should be taken in this regard:

* Minimize the amount of dust that escapes from processing equipment and ventilation systems.
* Install a Dust Collection System and monitor it closely to ensure it is operating properly.
* Where possible, install materials (Surfaces) that collect dust poorly and facilitate easy cleaning.
* Inspect and note all hidden or concealed spaces where dust accumulation might occur.
* Maintain a set schedule for cleaning all dust prone areas, and follow it closely.
* Use cleaning methods that do not themselves generate dust clouds when ignition sources are present.
* Locate Relief Valves away from dust hazard zones.
* Maintain a comprehensive dust control program, with hazard dust inspections, testing, housekeeping, and control initiatives.

In several of the cases highlighted earlier, the initial explosion spread by means of ductwork that connected various equipment (usually the Dust Collection System, and/or different parts of the ventilation system) throughout the plant. It is therefore vital that these ductwork systems be fitted with isolation values and inspected regularly to remove excess sitting dust accumulations.

Additionally, certain dust generating operations (such as the use of abrasives, blasting, grinding, or buffing) fall under OSHA  (or similar governmental agencies) ventilation requirements.

Ignition Control

Along with Dust Control, controlling all possible ignition sources also plays a major role in any comprehensive Dust Control Program. Along with Electrical Considerations, there are many other areas that merit attention with regard to ignition potential. Here are several key recommendations for controlling possible Dust Ignition sources.

* Proper Installation, Classification, Operation, and Maintenance of all Electrical Equipment and Wiring (Class II wiring methods and equipment such as “dust ignition-proof” and “dust-tight” should be employed)
* Employ adequate Static Electricity control methods such as Grounding Wires/Rods, etc.
* Limit Smoking, Open Flames, and Sparks in work area.
* Limit or isolate sources of mechanical sparks and friction
* Separate foreign materials that may ignite combustibles from process materials.
* Limit contact between heated surfaces and heating system from combustible dusts.
* Install spark arrestors/spark traps in all dust collector ductwork.

Further resources including US regulation, guidelines, and recommendations can be found in the following sources:

* OSHA’s Powered Industrial Trucks standard (29 CFR 1910.178).

Damage Control

Despite the best efforts of all parties involved, incidents may still occur. It is therefore, the wise course of action is to prepare for the worst, and implement a strategy that will reduce the severity of such an incident should it occur. The following is a list of recommended steps to take to minimize the impact of a Dust Explosion:

* Separate, and Segregate the Hazard to the extent possible. Place distance between the hazard and the work area, and isolate the hazard with barriers where possible.
* Install deflagration venting.
* Install pressure relief valves on applicable equipment.
* Employ Spark/Ember detection systems, and extinguishing equipment.
* To the extent possible, install explosion protection system, including sprinkler systems, and other assorted specialized suppression techniques.

Proper Employee & Management Training

Even with all of the aforementioned precautions, without a workforce, both employees and management, that have been properly educated about the dangers of Dust Explosions, and safety procedures to reduce the likelihood of their occurrence, and control, and limit the damage should they occur, there still remains high degree of probability for a Dust Explosion occurring.


Workers that are trained in preventing, and proper incident response techniques are integral to the safe operation of any facility. They are the people closest to the hazard, if these ones are trained to recognize and prevent these types of occurrences from taking place, they can accomplish much in this regard. These ones should also be encouraged to feel free to report unsafe working conditions, or areas where there could be an improvement in safety standards. Therefore all employees, whether they are working directly in hazard areas or not, should be adequately trained in safe work practices applicable to their job tasks, as well as on the overall plant programs for dust control and ignition source control. Periodic refresher courses should also be arranged to keep these safety issues fresh in their minds, and up to date with any possible changes to the hazard conditions themselves.


A qualified team of managers should be responsible for conducting a facility analysis (or for having one done by qualified outside persons) prior to the introduction of a hazard and for developing a prevention and protection scheme tailored to their operation. Supervisors and managers should be aware of and support the plant dust and ignition control programs. Their training should include identifying how they can encourage the reporting of unsafe practices and facilitate abatement actions.


The dangers of Dust Explosion are quite real; they have caused great amounts of damage to property, and have cost many lives. The importance of implementing a comprehensive dust control program, including hazard analysis, implementation of proven dust control and ignition control techniques, damage mitigation, and employee and management training cannot be overstated.

View this video report by the CSB

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