Hazard · draft · confidence 0.88
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Explosion hazard arising when fine coal particles (typically <75 μm) are suspended in air at sufficient concentration and ignited. Coal dust explosions can be initiated by a primary ignition source and propagate through entire coal handling areas, including conveyor tunnels, coal silos, and crusher buildings.
Exposure routes
- Blast overpressure and fragmentation from structural failure
- Thermal burns from fireball
- Inhalation of hot combustion products and carbon monoxide
Mechanism
Bituminous coal dust dispersed in air forms an explosive aerosol when particle concentration is between the lower explosive limit (~40–100 g/m³ for coal dust) and upper explosive limit. Ignition by a spark, hot surface, flame, or smoldering ember initiates rapid combustion of the particle surfaces. The heat released expands gases rapidly, creating an overpressure wave. In confined structures this wave can lift settled dust from surfaces, creating a secondary (often larger) explosion. Coal volatile matter content amplifies explosion severity: higher volatile matter → more rapid combustion.
Mitigations
- Dust suppression: water misting, foam, or oil at transfer points, crushers, and conveyors
- Explosion venting: burst panels on silos and enclosed conveyor tunnels sized to relieve overpressure
- Housekeeping: regular removal of settled dust from surfaces; no dust accumulation >1/8 inch (OSHA guideline)
- Explosion suppression systems: chemical suppression triggered by pressure sensors in high-risk enclosures
- Inert gas blanketing (CO₂ or N₂) in coal silos during storage
Severity
High. Coal dust explosions have caused multiple fatalities and extensive plant damage in mining and industrial settings. Primary explosions of limited scale can initiate catastrophic secondary explosions propagating through interconnected handling areas.
Warning signs
- Visible coal dust accumulation on surfaces and equipment
- High particulate readings in enclosed handling areas
- Smoldering coal in storage (self-heating indicator)
Connections
Incoming
- Has hazard ← Cokemaking — Coal handling and crushing areas generate fine coal dust; dust suppression and ventilation required.
- Has hazard ← Coking Coal — Fine coal dust generated during crushing and handling of coking coal can form explosive clouds; also causes coal workers’ pneumoconiosis.