Grain Dust ExplosionsHazard DefinitionNearly any finelydividedorganic substance becomes an explosive material when its dispersed as airsuspension hence, a very fine flour found in grain handling facilities can potentially becomedangerously explosive in air suspension.Exposure Conditions/Scenarios/Causal PathwayElements needed for a fire (the familiar "Fire Triangle"):[9]1. Combustible dust (fuel)2. Ignition Source (heat) and3. Oxygen in air (oxidizer).Additional elements needed for a combustible dust explosion:1. Dispersion of dust particles in sufficient quantity and concentration and2. Confinement of the dust cloudFalls from heightsHazard DefinitionIn 2011, the Bureau of Labor Statistics (BLS) reported a nonfatal,fallrelatedinjury rate of 48.2 per100,000 workers in the agricultural industry (a rate higher than reported for the transportation, mining,or manufacturing industries). Additionally, the BLS reported 167 worker fatalities in the agricultureindustry between 2007 and 2011.Falls from height can occur throughout a grain handling facility. Data has illustrated that relatively short falls, from 12 to 20 feet, can be fatal.Examples of surfaces that could present a falling hazard to grain handling employees might include floors, machinery, structures, roofs,skylights, unguarded holes, wall and floor openings, ladders, unguarded catwalks, platforms and manlifts. Additionally, workers are alsoexposed to potentially fatal falls as they move from the vertical exterior ladders on grain bins to the bin roof or through a bin entrance.[10]Between 1985 and 1989, falls from heights were the second leading cause of grainhandlingworker fatalities [2]. Falls from machinery andstructures were the second largest single cause of grainandsilagehandlingfatalities between 1985 and 1989 falls from structures accountedfor 79 percent of these fatalities [2]. Data has illustrated that relatively short falls, from 12 to 20 feet, can be fatal.Amputations from Grain Handling EquipmentHazard DefinitionMechanical equipment within grain storage structures, such as augers and conveyors, present serious entanglement and amputation hazards.Workers can easily get their limbs caught in improperly guarded moving parts of such mechanical equipment.Exposure Conditions Scenarios/Causal PathwaysWhile many pieces of equipment may possess safety features such as guards, covers, and shields that are designed to protect individuals frompotential amputations or other related injury, workers increase injury exposure when attempting to disable protective featuresAirborne contaminantsHazard DefinitionGrain storage structures can develop potentially hazardous atmospheres due to gases produced from spoiling grains and/or fumigation.Fumigants in grain storage bins are commonly used for insect control. Exposure to fumigants can cause central nervous system damage, heartand vascular disease, and lung edema as well as cancer. In addition to the direct health risks associated with fumigant exposure, exposureto these gases can also result in worker incapacitation and subsequently suffering injury from falling or suffocation from engulfment. Grainfacility workers involved with handling fumigants and/or fumigated grain are exposed to these potentially hazardous contaminants.[11]Fermenting or molding grain produce nitric oxide (NO), and also compounds known to be respiratory irritants such as nitrogen dioxide (NO2)and nitrogen tetroxide (N2O4). While low NO2 concentrations can cause coughing, labored breathing, and/or nausea, high concentrations cancause fluid to fill the lungs, which can result in death.Exposure Conditions/Scenarios/Causal PathwaysHazardous gas concentrations are generally highest within the first 48 hours after silage has been added to the container, but may still bepresent for roughly four weeks. The hazardous gases produced from fermenting silage (NO2 and NO4) are heavier than air and typically can bereduced in silos by means of opening the containers chute doors. Even when airing out the bin, potentially fatal concentrations of these gasesmay still exist in collections in confined spaces the air space between the bottom of the silo chute door and the top of the silage. Workers canbe exposed to hazardous gases, and could even inhale fatal doses of the contaminants if they fall, or bend over to work or pick up a tool, oreven if the gas is stirred up by a draft or the workers' activity.Exposed Systems and PopulationsYoung WorkersOf all recorded cases of grain engulfment, more than 60% of these cases occur at facilities that are not subject to OSHA regulations, mainly atfamily onfarmgrain storage units. Of all recorded cases of grain engulfment at OSHAexemptfacilities, 70% of those cases involvechildren.[12] The Department of Labor proposed, in 2011, sweeping regulations that would prohibit underage workers from entering grain silosand other hazardous activities.[13] Another study found that roughly one in five grain entrapments involve a child [14]Mitigating RiskEntrapmentAgricultural organizations have worked to protect their workers by improving entrapment and other confined space rescue techniques, as wellas by advocating increased awareness among farmers of engulfment prevention methods. Primary among these is a federal regulation thatforbids opening an auger or other opening at the bottom of a grain storage facility while someone is known to be "walking down the grain"within. Workers entering a grain bin should be equipped with a body harness which is tethered to a lifeline manned by at least two otherindividuals outside of the bin. Workers should never enter a bin of flowing grain. Exercise caution and be aware of grain quality beforeentering a bin. Lock out/tag out any and all power equipment (such as augers) before entering the bin.[15]Dust ExplosionsGood housekeeping practices, specifically the elimination of potentially combustible dust accumulation, can help mitigate the probability of anexplosion to occur. OSHA recommends grain handling facilities identify potential explosion contributors through conducting a thoroughhazard assessment of:All materials handledAll operations conducted, including byproductsAll spaces (including hidden ones andAll potential ignition sourcesTo prevent dust explosions and fires, employers must (among other things): Develop and implement a written housekeeping program withinstructions to reduce dust accumulations on ledges, floors, equipment and other exposed surfaces. Identify "priority" housekeeping areas ingrain elevators. The "priority" housekeeping areas include floor areas within 35 feet of inside bucket elevators, floors of enclosed areascontaining grinding equipment and floors of enclosed areas containing grain dryers located inside the facility. Dust accumulations in thesepriority housekeeping areas shall not exceed 1/8th inch. Employers should make every effort to minimize dust accumulations on exposedsurfaces since dust is the fuel for a fire or explosion, and it is recognized that a 1/8 inch dust accumulation is more than enough to fuel suchoccurrences. Inside bucket elevators can undergo primary explosions. OSHA's grain handling standard requires that belts for these bucketelevators purchased after March 30, 1988 are conductive and have a surface electrical resistance not exceeding 300 megohms. Bucketelevators must have an opening to the head pulley section and boot section to allow for inspection, maintenance, and cleaning. Bearings mustbe mounted externally to the leg casing or the employer must provide vibration, temperature, or other monitoring of the conditions of thebearings if the bearings are mounted inside or partially inside the leg casing. These bucket elevators must be equipped with a motion detectiondevice which will shutdownthe elevator when the belt speed is reduced by no more than 20% of the normal operating speed. Implement apreventative maintenance program with regularly scheduled inspections for mechanical and safety control equipment, which may include heatproducing equipment such as motors, bearings, belts etc. Preventive maintenance is critical to controlling ignition sources. The use of vibrationdetection methods, heat sensitive tape or other heat detection methods can help in the implementation of the program. Minimize ignitionsources through controlling hot work (electric or gas welding, cutting, brazing or similar flame producing operations). Install wiring andelectrical equipment suitable for hazardous locations. Design and properly locate dust collection systems to minimize explosion hazards. Allfilter collectors installed after March 1988 shall be located outside the facility or located in an area inside the facility protected by an explosionsuppression system or located in an area that is separated from other areas by construction having at least a one hour fire resistance rating andwhich is located next to an exterior wall vented to the outside. Install an effective means of removing ferrous material from grain streams sothat such material does not enter equipment such as hammer mills, grinders and pulverizers.