Engulfment happens within seconds, typically when workers are inside the grain bin while augers or vacuums are in operation and creating “flowing grain. Grain flows rapidly from a 10-inch auger,” he said. “Flow rate may be 68 bushels per minute. That means a person who is 6-feet-tall and 165 pounds will be entrapped within five seconds to the point that he cannot free himself. Within 25 seconds, he will be completely engulfed.”

The key for survival in that short window is to stop the grain from flowing as quickly as possible. Persons trapped in grain, even if they are not completely covered, may die of suffocation from the pressure exerted by the grain. “One foot of grain over an individual’s entire body weighs about 300 pounds.” With that much pressure, extracting the worker without causing serious injury is difficult.

Smith said unloading operations offer significant risks. Also, grain bridges, surfaces that have crusted over leaving cavities underneath, may collapse and trap workers. Grain masses adhering to side walls also pose hazards of breaking away and engulfing workers inside the grain bin.

Poorly conditioned grain is a contributing factor. Grain put up too wet may begin crusting and create those bridges or adhere to walls. When the grain is unloaded, those structures have to be broken up to allow the grain to flow. In many cases, that means workers enter the bins to “walk down the grain,” to keep it flowing. “That’s when workers become engulfed.”

The ideal solution to bridges and other in-bin grain problems is to use tools to break up the grain. With someone inside a bin, augers and vacuums should be shut down and proper communication established with an observer at the bin entrance and with someone on the ground.

“With augers or vacuums in operation, the equipment operator outside often cannot hear cries for help,” Smith said.

Risk factors inside a grain bin are numerous and include the speed of the flowing grain, the force of the grain on a body and presence of dangerous gases. “Molds, fungi and bacteria may create problems,” Smith said. “Also, gases such as carbon dioxide, nitrous oxide and others may build up in grain bins.

“Time and pressure are important. When a worker becomes trapped to his knees he can’t escape without assistance. And movement may cause him to sink deeper and deeper. As grain keeps moving it quickly forms a cone of depression.”

A person weighing 165 pounds will require 900 pounds of force to lift him out of the grain if he is fully submerged. “Extraction often is necessary from awkward positions and may result in serious injury. Training and safety equipment are necessary.”

Most engulfment cases—68 percent—occur in corrugated metal grain bins. Transportation may result in engulfment and usually involves grain wagons. Some cases occur in semi-trailers and rail cars.

Excess moisture in the grain is a prime contributing factor to grain engulfment, Smith said. Other factors include excess fines and foreign material in the grain, out-of-condition grain, engaged unloading equipment (with workers inside the bin), entering a grain bin, unsupervised children in exempt workplaces, increased on-farm storage, unfamiliarity with extraction procedures, lack of safety features in older storage structures and an inability to install proper safety equipment —harnesses—in older facilities.

Smith said prevention is essential. “Signs are not enough. Owners and managers must make safety a priority. No shortcuts should be allowed.”