Staying safe in the silo

No one would be surprised to hear that there are lots of government rules concerning industrial workspaces. It’s the job of bodies like the U.S. Occupational Safety and Health Administration (OSHA) to make regulations that keep workers safe. It might surprise you though, to learn that — at least in terms of workplace safety — farms are considered to be industrial.

Among the myriad regulations designed to keep farmworkers out of danger is an extensive list of OSHA requirements for running and/or working around grain bins and silos, the enormous structures in which harvested grain is stored.

So, what is it about stored grain that requires such an abundance of caution?

Hidden hazards

For one thing, harvested grain is extremely dusty, and grain dust in a confined space like a silo or elevator can create an explosion hazard. If the confined dust becomes airborne inside the storage facility and meets a source of heat — a static charge, for instance, or a bearing burning out in an elevator’s machinery — the dust can ignite, producing a chain reaction of explosions that can damage or even blow the storage vessel apart and injure or kill anyone unfortunate enough to be too close.

Then there is the danger of fire. If mold begins to grow in stored grain, it can envelop the grain kernels, binding them together into an ever-growing mass. Mold spores feeding on the grain’s starches and oils produce water, carbon-dioxide, and heat, creating a hot spot in the center of the mass. If insects have infested the grain, this heating process can accelerate. As long as oxygen can’t get to this heated mass, it may remain inert. But that can quickly change if the grain is disturbed, as it is when it’s unloaded from storage.   

There’s also the danger of engulfment. We’ve all seen the movie: an explorer, making his way through the heart of darkness, takes a misstep and finds himself swallowed in quicksand.

That’s scary, but that’s Hollywood, and scenarios like this seldom happen in real life. However, if you shift the map coordinates from the jungle to the heartland and set the scene in a grain bin, then the danger is real, and incidents like this are far too common. According to research compiled in the Purdue Agricultural Confined Spaces Incident Database (PACSID), between 1962 and 2020 there were 2,404 cases of grain engulfment. Sixty percent of these cases were fatal.

More about engulfment

In cases of engulfment, a farm worker literally drowns in grain. This most often happens when the unwary or unprotected worker enters a storage structure to solve a problem. For instance, a worker may climb through the hatch at the top of a silo to unclog a downspout. Meanwhile far below, another worker starts a grain auger to empty the vessel. The entire mass of grain begins to shift, making it extremely difficult for a worker to get out. In less than 30 seconds they may be completely buried.

Engulfment can also occur when the process of emptying the silo has been stopped and started several times, causing a grain bridge to form. This condition, in which mold or freezing has caused the top layer of grain to form a deceptively hard, thick crust, may convince the worker that it’s safe to walk on it, and it may even bear the worker’s weight briefly.

But the bridge can collapse, dropping them into the loose grain below.  Workers can also be imperiled when damp or moldy grain has formed steep columns against a bin wall, leaving a void in the middle. An unwary worker might enter this void to dislodge the grain with a rake, only to be buried when the grain wall collapses in an avalanche.

Learn more about best safety practices for working in and around grain bins, and find more sources for information, in Grinnell Mutual’s downloadable “Worker Entry into Grain Storage Bins” loss control bulletin.

You can also see a trailer of the independent film “Silo,” an affecting story about a frightening grain bin experience and learn how to get a DVD or host a screening in your community.

For more information about farm safety, visit our farm safety tips and resources.

Sources: osha.gov; Kansas State University Department of Grain Science; Oklahoma State University Extension Service; Purdue Agricultural Confined Spaces Incident Database

Find farm coverage Find an agent near you