45 Intro to Combustible Dust Hazards 1 Dust Can Combust What Is Combustible Dust? Combustible dust is: • Comprised of small, solid organic particles Dispersed so that it creates a potentially explosive atmosphere Dusts are created by: • Transporting, handling, processing • Grinding, polishing, milling, or shaping • Abrasive blasting, cutting, or crushing Mixing, sifting, or screening dry materials • Buildup of dried residue from the processing of wet materials How Does Dust Combust? In order for dust to combust, certain conditions must exist. Required Conditions Five Elements of a Dust Explosion Ignition Sources - Chain Reaction Required Conditions Dust settles and accumulates on horizontal surfaces, such as: • Floors - Exposed beams and rafters - Equipment If this dust is disturbed and forms a cloud, it may easily become ignited, resulting in a rapid explosion. Five Elements of a Dust Explosion For a dust explosion to occur, five conditions must be present: • Fuel source (dust) - Ignition source (spark, flame, or hot surface) - Oxygen to support combustion Dispersion of the dust - Confinement of the dust cloud Ignition Sources Potential ignition sources within the workplace Include: • Flames and hot surfaces • Friction from machinery or material movement (sparks, heat, or static electricity) • Dust in switches or electrical gear Additionally, some organic materials are prone to spontaneous combustion. Chain Reaction The biggest danger of dust explosions is that they are typically the result of a chain reaction that occurs virtually instantaneously. 1. Initial deflagration creates a shockwave 2. Dust is disturbed and dispersed 3. Ignition of resulting dust cloud and secondary deflagration Dust Hazards The components of the dust pentagon you have the most control over are: • Fuel - dust accumulation Dispersion - how dust becomes airborne Ignition source - spark, flame, or hot surface Preventing Dust Hazards There are actions you can take to help prevent dust hazards. Watch for Buildup - Remove Dust Safely - Watch for Ignition Sources - Maintain Filtration Watch for Buildup To help prevent hazards, watch for buildup of dust on horizontal surfaces, such as overhead pipes and rafters, and the accumulation of dust in your work area. Report accumulations in difficult to access areas to your supervisor. Remove Dust Safely Follow safe housekeeping practices; do not aggressively dry-sweep dust or use compressed air to blow away dust buildup-doing so will disperse dust into a potentially explosive cloud. Use a vacuum system rated for explosive environments to remove dust. Watch for Ignition Sources Be conscious of ignition sources like hot surfaces, open flames, and sparks. Keep electrical outlets, switches, and breaker panels free of dust accumulation. Maintain Filtration Inspect and maintain filter units and ventilation systems. Performing routine maintenance ensures the proper function of equipment to control the presence of dust.
