Grain entrapment, or grain engulfment, occurs when a person becomes submerged in grain and cannot get out without assistance. It most frequently occurs in grain bins and other storage facilities such as silos or grain elevators, or in grain transportation vehicles, but has also been known to occur around any large quantity of grain, even freestanding piles outdoors. Usually, unstable grain collapses suddenly, wholly or partially burying workers who may be within it. Entrapment occurs when victims are partially submerged but cannot remove themselves; engulfment occurs when they are completely buried within the grain. Engulfment has a very high fatality rate.
While the death rate from workplace accidents on American farms has declined in the first decades of the 21st century, grain-entrapment deaths have not, reaching an all-time annual high of 31 deaths in 2010. Many of those victims have been minors. Agricultural organizations have worked to protect them and improve rescue techniques, as well as spread awareness among farmers of prevention methods. Primary among these is a federal regulation that forbids 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.
Smaller family farms, however, are exempt from most federal labor regulation specific to agriculture, and no safety regulations govern children working for their parents. In 2011, the U.S. Department of Labor proposed sweeping new regulations that would have changed this, prohibiting underage workers from entering silos, among other provisions. They were withdrawn after protests from farmers and politicians of both U.S. parties.
Occurrence
At some grain-handling facilities, employees "walk down the grain" on top of it to expedite the flow of grain from the top when it is being allowed to flow out the bottom. This is the most common cause of grain entrapments. Regulations issued by the United States Occupational Safety and Health Administration (OSHA) specifically forbid this at larger commercial facilities subject to them; most smaller farms are not. It may also be necessary to enter a grain storage facility to remove damp, clumped grain (usually from early spoilage) stuck on the walls. Entrapments have also occurred to children in grain transportation vehicles, or to those outside when grain is released from a storage facility or next to large freestanding grain piles.
Workers in the grain can become entrapped in three different ways: an apparently stable surface may in fact be a "grain bridge" over an area beneath which the grain has already settled; a vertical mass of grain settled against a wall may suddenly give way while being cleared; moving grain will not support the weight of an average person.
Once entrapment begins, it happens very quickly due to the suction-like action of the grain. Researchers in Germany found that an average person who has sunk into grain once it has stopped flowing can get out only as long as it has not reached knee level; at waist level assistance is required. Once the grain has reached the chest a formal rescue effort must be undertaken., cited at
Half of all entrapment victims eventually become engulfed. A human body in grain takes seconds to sink, minutes to suffocate, and hours to locate and recover. Recovered bodies have shown signs of blunt force trauma from the impact of the grain; one victim was found to have a dislocated jaw.
At a depth of , the lateral pressure of grain, as experimentally measured by load cells placed against bin walls, is ; at it is , which appears to be its maximum. While those pressures are less than water at equivalent depths, they are measurements of active pressure against bin walls rather than the passive pressure a body would experience, which is always greater. A victim trapped horizontally faces greater pressures, at and at .
That pressure can make it difficult to breathe even when the victim's airway is unobstructed; it increases with every inhalation, making it more critical to secure breathing space for a victim in that situation. It has been likened to concrete, cement or quicksand; and described as making it impossible to even wiggle toes inside a shoe or boot; one survivor said he felt as if an " semi truck had parked on [his] chest." The compression also makes it hard for blood to circulate, reducing the oxygen that gets to cells and increasing the amount of toxins in the system.
Suffocation rarely occurs from the weight of the grain, but rather from the grain itself. If a victim's airway remains unobstructed, or they find an air pocket within the grain, they may be able to keep breathing and be rescued; the 40–60% porosity of stored grain makes it at least theoretically possible. In one instance a trapped person was able to survive for three hours. In 2013 an Iowa man wearing a battery-powered mask that filtered out dust, a result of his asthma, was engulfed below the surface of of corn in an bin. The respirator mask enabled him to survive, drifting in and out of consciousness for five hours until he was rescued by draining the bin slowly after efforts to pull him through the rope he was attached to failed. At that time, his heart rate was 173 beats per minute, near his maximum; he was hospitalized for two days afterwards.
Rescue
Several factors complicate the rescue of entrapment victims even if their heads remain above the grain. Most grain storage and handling facilities are located on farms in rural areas, often distant from trained rescuers such as fire or ambulance services. They are also confined spaces, posing hazards to rescuers.
Foremost among them is the air within. Carbon dioxide or toxic gases, such as nitrogen oxides, accumulate from spoiling grain. They can cause asphyxiation in great enough concentrations without proper ventilation of the area. The dust can also sometimes have molds or spores that may be toxic or cause allergic reactions. There is at least one documented instance of a first responder requiring treatment as a result of such inhalation; rescuers are advised to wear at least dust masks or even self-contained breathing apparatus (SCBA).
North Dakota State University (NDSU) advises farmers that as soon as an entrapment occurs, in addition to immediately notifying local emergency services, the workers at the facility be required to shut off anything causing motion in the grain, or close any outlet. Turning on the aeration fan, without any heat source activated, improves ventilation. NDSU warns rescuers to take care not to make the situation worse, and not to take action that would result in they themselves becoming entrapped or engulfed. Proper safety equipment, such as lifelines, is required for a rescue. Experts advise that no more than two should walk on the surface of the grain at any time.
Temperature extremes can cause problems for both rescuers and victims. Stored grain is often kept fresh by blowing dry air over it. This, combined with any moisture in the grain, can chill its core to . creating a risk of hypothermia for the victim, especially one fully engulfed. Conversely, the air within the bin may be warmer than usual due to the heat released by decaying grain, the lack of exterior ventilation (especially on hot days) and any rescue activity; there is thus a risk of heat illness for those trying to free the victim. During the five hours it took to rescue the man trapped in Iowa, it was estimated that temperatures in the bin reached , more than above that day's reported high. Firefighters carrying out the rescue were monitored closely and made to take periodic breaks; even so, one experienced heat exhaustion.
Even if a living victim is roped, they cannot simply be removed that way. Grain creates friction that resists the force used to pull them out. It requires to lift a victim buried up to their waist; removing a human completely trapped in grain takes . These forces are above the level that can cause permanent spinal column injury. Some rescue attempts using ropes connected to tractors to pull victims out have resulted in separated shoulders.
Rescues of an entrapped victim usually entail building makeshift retaining walls in the grain around them with plywood, sheet metal, tarpaulins, snow fences or any other similar material available. Once that has been done, the next step is creating the equivalent of a cofferdam within the grain from which grain can then be removed by hand, shovel, grain vacuum or other extraction equipment. Purpose-built plastic grain rescue tubes are also available for this purpose; using them causes an increase in pressure around the victim, possibly by increasing the bulk density of the grain within the tube, which in turn requires more force to pull them out until the grain surrounding them is removed."Extrication Forces", 76–78
While some of these techniques have been used to retrieve engulfed victims or their bodies as well, in those cases it is also common to cut a hole, or attempt to, in the side of the storage facility; this requires consulting an engineer to make sure it can be done without compromising the facility's structural integrity; usually by cutting high up and in a uniform pattern around the side of the bin. It is also possible that this can suck the trapped person deeper into the grain. This appears to be most effective in facilities with a capacity of or less. There is also the possibility of a dust explosion, although none are known to have occurred yet during a rescue attempt.
Survivors of grain entrapment also may require treatment. Many develop painful contusions from the pressure of the grain they were confined in; it is not uncommon for them to lose consciousness due to the drop in blood pressure as circulation returns to normal. Glenn Blahey, president of the Canadian Agricultural Safety Association (CASA), recalls one incident where a man rescued from a Manitoba grain bin had to be immediately hospitalized as he went into a coma for several days afterwards due to the toxins that had built up in his bloodstream as a result of the oxygen deprivation that occurred during the hours it took to rescue him.
Rescued victims have also experienced psychological issues. The survivor of a 2010 Illinois entrapment that killed both his coworkers experienced survivor guilt, with accompanying insomnia, and turned to heavy alcohol and marijuana use to deal with it. Feeling himself to be his town's "Bubble Boy", he did not return to work at the facility where it happened, instead taking a job at a local grocery across the street from the bin he was entrapped in, where the holes cut during the rescue were still visible. A Brazilian entrapment survivor says he was fired by his employer after refusing to return to work in the bins and asking to be assigned elsewhere in the company's operations.
Prevention
The best way to prevent grain entrapments is zero entry: the near or complete elimination of any reasons to enter a grain storage facility. This can be accomplished primarily by storing grain properly. If kept at the proper moisture level of 14 percent or less and protected from the elements, grain will not form the kind of clumps that create grain bridges or other areas of unequal density within and require clearance.
Entrapments are more likely when grain is more spoiled. "Coring" grain by removing some of it from the center after the facility has been filled also reduces spoilage since it generally takes the broken and smaller grains where insects tend to grow within. The University of Iowa's Great Plains Center for Agricultural Health (GPCAH) advises that any clearing of clumped grain be done from outside using a long pole.