Ignoring combustible dust hazards can lead to hefty fines and high risks for injury

Employers should examining their facilities for potential hazards related to dust explosions.

Employers should examining their facilities for potential hazards related to dust explosions.

An upstate New York manufacturer has been issued nearly $200,000 in potential fines after an investigation by the Occupational Health and Safety Administrations found workers were exposed to uncorrected explosion hazards and recurring fire and fall hazards..

“Combustible dust is an explosion hazard that can affect many industries.”

The Albany Area OSHA Office uncovered the violations in a follow-up investigation after the manufacturer failed to verify it had corrected hazards uncovered in a previous inspection. Inspectors identified several new and recurring hazards, including:

  • Unmanaged combustible dust
  • Fire and explosion risks related to conveyor equipment
  • An inoperable spark detection/fire suppression system
  • Fire extinguishers that had not been annually inspected or kept in fully charged and operable condition.
  • Accumulations of combustible wood dust and shavings on rafters and other surfaces.
  • Piles of wood dust and shavings on floors that create fire, slip, trip and fall hazards

All told the violations resulted in $197,820 in potential fines. Albany Area Director Robert Garvey noted the violations were especially concerning because the combustible dust had led to a significant fire that occurred in the plant’s production area since OSHA’s previous inspection.

Understanding the combustible dust hazard
Combustible dust is an explosion hazard that can affect many industries. As OSHA explained, any combustible material can burn rapidly when in dust form. When the dust is suspended in air, it may, under the right concentration and conditions, become explosive. This can be true even for materials that do not burn in larger pieces, such as aluminum or iron.

This hazard is common in industries including construction, chemical manufacturing, furniture, textiles, fossil fuel power generation, recycling operations and metalworking. However, given the wide range of materials that can become combustible in dust form, employers across all sectors need to be aware of the risks. Common combustible materials include:

  • Baking ingredients including sugar, spice, starch and flour
  • Agricultural products such as feed, grain and tobacco
  • Plastics
  • Wood, paper and pulp
  • Rubber
  • Pesticides
  • Pharmaceuticals
  • Dyes
  • Coal
  • Metals, especially aluminum, chromium, iron, magnesium and zinc

Combustible dust is also a concern because of the high occurrence of explosions and related injuries. From 1980 to 2005, the U.S. Chemical Safety and Hazard Investigation Board identified 281 combustible dust incidents that contributed to 119 work site fatalities, 718 injuries and extensive damage to several industrial facilities.

“Combustible dust is also a concern because of the high occurrence of explosions and related injuries.”

As OSHA noted, combustible dust fires and explosions are caused by a combination of factors. In addition to the presence of a combustible material in small form, there must also be an ignition source and oxygen in the air. For an explosion to occur, the dust particles must be dispersed in a sufficient quantity and concentration, and the dust cloud must be confined so that it cannot disperse.

If the dust cloud is ignited within a confined or semi-confined area, such as a building, it will burn very rapidly and may explode. This presents a powerful threat to worker safety as the explosion is likely to result in fires, additional explosions, flying debris and possibly collapsing building components. The initial explosion may also release additional combustible dust into the air, resulting in a second fire or explosion. In many instances, the secondary explosion is more destructive than the primary explosion due to an increase in the quantity and concentration of combustible dust.

How to control the risks of combustible dust
In order to control the potential for a combustible dust fire, employers must first begin with examining their facilities for potential hazards related to dust explosions. This can be done by identifying:

  • All materials at the work site that may become combustible when finely divided;
  • Processes that use, consume or create combustible dusts;
  • All areas where combustible dusts may accumulate;
  • Any processes, machines or other means that may disperse the dust in the air, such as a fan
  • Potential ignition sources

When identifying combustible dusts that may be present at the job site, employers can consult the International Code Council’s International Fire Code and National Fire Protection Association’s Uniform Fire Code. The NFPA also offers specific standards relating to combustible dust, including standards 654 and 484. Employers should also be aware variables including particle size, shape and moisture content can affect the combustibility of a material.

“Employers must first examine their facilities for potential hazards related to dust explosions.”

Employers should also determine if electrical equipment in areas of the facility potentially containing combustible dust will require special electrical equipment classification. In these instances, special equipment or wiring methods may be necessary to reduce the risk of ignition of dust from sparking. OSHA offers additional guidance in its Electrical standard as does NFPA 70 and 499.

To avoid accumulation of combustible dust, the NFPA offers several recommendations for employers, including but not limited to:

  • Keeping dust out of process equipment or ventilation systems that may spread it to other areas of the facility;
  • Using dust collection systems and filters;
  • Utilizing surfaces that minimize dust accumulation;
  • Conducting regular inspections and cleaning to discover and remove dust residues;
  • Using only cleaning methods and machines that do not generate dust clouds and are specifically designed for dust removal
  • Developing and implementing a formal system for hazardous dust inspection, testing, housekeeping and control
  • Allowing OSHA inspectors full access to all areas of the facility to check for hazards

Ignition controls should also be introduced to lower the risk that dust accumulations lead to fire or explosion. In addition to using proper electrical equipment and wiring methods, employers should eliminate common ignition sources such as static electricity, smoking, open flames and sparks from areas with combustible dust. Additionally, employers must look at risks presented by industrial trucks, cartridge activated tools, heated surfaces and heating systems and isolate these machines from combustible materials when applicable. All equipment must also be properly maintained as malfunction may contribute to sparking.

Employers are also advised to create systems that will control any damage and reduce the risk of injury if an explosion or fire does occur. OSHA recommends several processes, including:

  • Isolating combustible dust from the rest of the work site through barriers or distance
  • Adding deflagration venting to areas containing combustible dust
  • Installing pressure relief venting on equipment
  • Using spark/ember detector systems and sprinkler or other extinguishing or specialized suppression systems

Finally, OSHA requires all employees exposed to combustible dust be trained to recognize and prevent the associated hazards. Employees should be empowered to recognize unsafe working conditions and taking preventative action or alert management.