Combustible materials can burn quickly. When in dust form, some can explode when suspended in the air in certain concentrations and under the right circumstances.
A wide variety of materials can be explosive in dust form. Some of these materials include tobacco, plastics, wood, paper, pulp, rubber, furniture, textiles, pesticides, pharmaceuticals, dyes, coal, metals, fossil fuels, and food such as sugar, spice, starch, flour, or feed.
The Occupational Safety & Health Administration (OSHA) advises employers to protect workers by identifying any combustible dusts in the workplace and developing plans and procedures to help prevent explosions. Facilities assessing the potential for dust explosions may find the following possible hazards:
• Materials that are explosive when in dust form
• Activities that use, consume, or produce combustible dusts
• Open and hidden areas where combustible dusts may build up
• Activities that cause dusts to spread into the air
• Potential ignition sources
Once these risk factors are identified, employers can help reduce the risk of fires and explosions by controlling dust and ignition sources and training employees to recognize and take action against hazards. Some guidelines offered by OSHA for controlling dusts include:
• Minimize the escape of dust from equipment, power tools, or ventilation systems by using dust collection systems and filters
• Use surfaces that are easy to clean and minimize dust accumulation
• Provide access to all hidden areas to allow for inspection
• Regularly inspect for dust residues in open and hidden areas
• Regularly clean dust residues
• When ignition sources are present, use cleaning methods that do not create dust clouds
• Only use vacuum cleaners approved for dust collection
• Position relief valves away from dust hazard areas
• Develop and put into effect frequent hazardous dust inspections, testing, housekeeping, and control programs, preferably in writing
OSHA also provides recommendations for controlling ignition sources that might cause combustible dusts to explode. Some of these recommendations are:
• Use proper electrical equipment and wiring methods
• Control static electricity, including bonding of equipment to ground, smoking, open flames, sparks, and friction
• Keep materials with the potential to ignite separate from dusts and process materials
• Keep dusts away from heated surfaces and systems
• Use industrial trucks and cartridge activated tools properly
• Ensure all equipment is properly maintained
Well trained employees can be the strongest line of defense against dust explosions. When the workers who are closest to potential hazards are educated on the risks of combustible dust, they can play an important role in recognizing unsafe conditions, taking precautions, and alerting management.
According to OSHA, damage and danger produced by an explosion can be minimized by isolating the hazard, proper venting of workspaces and equipment, installing explosion protection, sprinkler, or specialized suppression systems, and providing spark and ember detection and extinguishing systems. Safeguard work crews against fires and explosions caused by combustible dust with the proper training, fire safety equipment, and first aid supplies.