Combustible dust, a hazard that has historically received little attention from employers and government agencies alike, is a hidden danger that every company operating a saw should address. Sawdust often goes unnoticed in all manners of nooks and crannies although it poses a major hazard if a secondary explosion occurs.
A dusty room by itself cannot set off an explosion. However, Daniel Horowitz, director of public affairs at the U.S. Chemical Safety Board (CSB), said that if enough dust accumulates in an area, an initial explosion can trigger a secondary dust explosion that can have catastrophic consequences.
According to the Occupational Safety and Health Administration (OSHA), dust has accumulated in many factories and triggered secondary explosions that have killed and injured hundreds of employees and caused hundreds of thousands of dollars in facility damage.
Five elements must be present for a dust explosion to occur. Known as the “Dust Explosion Pentagon,” these elements include oxygen, heat, fuel, dispersion and confinement. Without all five elements, an explosion cannot occur.
So exactly where does the dust come into play? An initial explosion in processing equipment or in an area where dust has accumulated may dislodge more piled dust into the air. If ignited, the additional dust dispersed into the air has the potential to cause one or more secondary explosions. These can be far more destructive than an initial explosion because of the increased amount and concentration of dispersed combustible dust.
David Dick, an attorney who handles OSHA-related cases, said the main issue regarding worker safety really has to do with sufficient education in the work place. While many companies have knowledge of OSHA standards, Dick said there are a lot of smaller companies with limited staffs that are not as familiar with the risk of combustible dust.
“From my point of view and my practice, that’s the biggest problem,” Dick said. “Half the time it’s ignorance.”
Others have a different take on the hazard. Critics contend that OSHA has been relaxed in terms of preventative measures to limit dust explosions.
Following a succession of serious combustible dust explosions in 2006, the CSB conducted a major study of combustible dust hazards. It identified 281 combustible dust incidents between 1980 and 2005 that proved fatal to 119 employees, injured 718 others, and extensively damaged industrial facilities. Earlier this year, a dust-related explosion at the Imperial Sugar refinery in Port Wentworth, Ga. killed 12 workers and critically injured 11 others. These events have helped raise awareness about the dangers of dust explosions.
OSHA has addressed the issue by publishing material to educate businesses about dust-related risks and preventative measures. Look at the sidebar associated with this article to see OSHA’s recommendations.
Some members of Congress are seeking further action beyond additional worker education. They want federal regulations to ensure that workers are not placed in jeopardy. In early May, the U.S. House of Representatives passed the Combustible Dust Explosion and Fire Prevention Act. This bill, if signed into law, would require the Secretary of Labor to issue interim and final occupational safety and health standards regarding worker exposure to combustible dust.
The Bush administration maintains that relevant combustible dust standards are in place and has threatened to veto any new regulations. OSHA officials deny the need for further rules pointing to the 17 existing standards that collectively provide protections against combustible dust hazards.
OSHA officials stated, “The Administration has serious concerns with the expedited and one-size-fits-all regulatory approach required by the bill, which will impact as many as 200,000 workplaces in a variety of industries throughout the United States.”
The requirements currently in place include regulations for housekeeping; hazardous locations; electric power generation, transmission and distribution; hazard communication; and grain handling. Additionally, when no OSHA standard addresses a specific hazard, OSHA officials can cite the general duty clause of the Occupational Safe & Health Act, which requires employers to provide workplaces that are free from recognized hazards likely to cause serious harm or death.
Wood companies should become aware of dust dangers even if Congress does not pass more stringent regulations. It all starts with conducting a combustible dust analysis of your current operations. For additional information on current regulations and advice on how to protect your employees, visit http://www.osha.gov/dts/shib/shib073105.html.
The following are recommendations created by OSHA to help protect your company from secondary dust explosions.
Dust Control Recommendations
• Implement a hazardous dust inspection, testing, housekeeping, and control program;
• Use proper dust collection systems and filters;
• Minimize the escape of dust from process equipment or ventilation systems;
• Use surfaces that minimize dust accumulation and facilitate cleaning;
• Provide access to all hidden areas to permit inspection
• Inspect for dust residues in open and hidden areas at regular intervals;
• If ignition sources are present, use cleaning methods that do not generate dust clouds
• Use only vacuum cleaners approved for dust collection; and
• Locate relief valves away from dust deposits.
Ignition Control Recommendations
• Use appropriate electrical equipment and wiring methods;
• Control static electricity, including bonding of equipment to ground;
• Control smoking, open flames, and sparks;
• Control mechanical sparks and friction;
• Use separator devices to remove foreign materials capable of igniting combustibles from process materials;
• Separate heated surfaces from dusts;
• Separate heated systems from dusts;
• Select and use industrial trucks properly;
• Use cartridge activated tools properly; and
• Use an equipment preventive maintenance program.
Injury and Damage Control Methods
• Separation of the hazard (isolate with distance);
• Segregation of the hazard (isolate with barrier);
• Deflagration isolating/venting;
• Pressure relief venting for equipment;
• Direct vents away from work areas;
• Specialized fire suspension systems;
• Explosion protection systems;
• Spark/ember detection for suppression activation;
• Develop an emergency action plan; and maintain emergency exit routes.
