Agricultural structures account for much of what we envision as an idyllic farm scene. In fact, it's almost impossible to picture a farmhouse without a barn and silo nearby.

Such structures are used to house livestock and store machinery, grains, animal feed and manure, but those innocent uses can mask a considerable variety of dangers. Such problems can be hazardous not only to the farm's workers and residents, but to the fire, rescue and EMS personnel who are called to the farm for emergency incidents.

The hazards faced by farmers and rescuers involving agricultural structures include falls from heights; electrocutions; entrapments in grain, feed, animal waste and machinery; hazmat exposures; IDLH atmospheres; and fires and explosions.

Several firefighters have been injured or killed during fireground and rescue operations at farm structures. These injuries and deaths typically result when responders aren't familiar with the structures and their hazards, or when rescuers fail to follow proper confined-space or firefighting procedures.

For example, many structures on farms qualify under one or more of the OSHA criteria for confined spaces. OSHA's confined-space standard, 29 CFR 1910, 146, defines a confined space as one that:

• Is large enough for someone of any size to enter and work,
• Has limited or restricted entry and exit, and
• Isn't designed for continuous occupancy.

A “permit-requiring” confined space has one or more of the following characteristics:

• Hazardous atmosphere.
• Material that could engulf an entrant.
• Internal configuration of inwardly converging walls or a sloped or tapered floor that could entrap or asphyxiate an entrant.
• Any other recognized serious safety or health hazard.

Even if a local fire-rescue agency hasn't made any written agreements with the owners or operators of such facilities to provide confined-space rescue, it's likely to be summoned to such an incident. As a result, every agency should have and follow a confined-space rescue plan, which includes risk assessment, pre-planning, choosing and purchasing equipment, establishing SOPS, and providing the necessary training to agency members. Fire-rescue crews must decide what level of confined-space rescue they can provide and then prepare for that level.

One of the more common confined spaces on a farm is the silo, where forage crops to be used for animal feed are stored for later use. Silos should not be confused with grain bins or grain elevators, which are used to dry and store grains like wheat, corn, oats and barley. They have different forms, and their own hazards.

Preplanning specific to silos is essential and should include the following:

• Type and brand of silo and silo unloader.
• Owner and manufacturer.
• Normal types of contents.
• Dimensions and age.
• Modifications, if any.

Common silos

Vertical, also called tower or upright silos, are the recognizable round cylinders on farmsteads. The fact that there are one million tower silos in North America, coupled with the multiple hazards of these structures, make silo rescue and firefighting an important issue for many rural rescuers. However, many farmers aren't using their tower silos in favor of larger trench and/or bag silos.

Vertical silos are subdivided into conventional, oxygen-limiting and modified. Each type presents different problems and challenges, so rescue personnel need to be able to distinguish between these types. Misidentifying a silo and employing incorrect procedures can result in needless injury or deaths of patients and rescuers.

Conventional silos are constructed from poured concrete, concrete staves (curved concrete blocks held in place by steel rings) or steel. Older ones were made of tile blocks or wood. Conventional silos usually can be identified by the 3-foot diameter chute that runs the height of the silo. However, some modified oxygen-limiting silos have been retrofitted with exterior unloading chutes. The chute allows the silage to fall down into the barn, wagon or conveyer during unloading operations. The silos may have no roof at all or a hemispherical domed roof.

Oxygen-limiting silos are designed to limit the amount of oxygen in the structure, a feature that can rapidly kill farm workers and rescuers. Farmers and firefighters have been injured and killed entering from both the top and the bottom of these silos. Many firefighters also have died when the oxygen-limiting silo exploded while they were on top of the structure during firefighting operations.

Oxygen-limiting silos are constructed of steel or poured concrete, with the blue-colored Harvestore brand being the most common. These silos generally have a flatter roof than conventional silos, and most will have roofs with two 18- or 24-inch openings. Unmodified oxygen-limiting silos have no exterior unloading chute, as they unload from the bottom.

Modified silos is a catch-all grouping of silos that have been modified from their original design. These modifications can change the tactics employed in rescue/recoveries and firefighting. One example of these silos is the oxygen-limiting Harvestore silo that is modified for top unloading with unloading doors and an exterior chute or center unloading design. Another example of a modified silo is the conventional silo that has a center unloading system that replaces the exterior chute.

Fire suppression

The deaths of firefighters during the suppression of an agricultural silo fire are a grim reminder of the need for education in farm emergencies. These tragedies, unfortunately, have occurred across the country numerous times. Firefighters must be very cautious and continually analyze the risks and benefits of each of their actions.

Silo fires usually occur when farmers fail to follow proper forage storage procedures. They also can occur at saw mills, where agricultural-type silos are used to store sawdust and saw chips. These fires produce carbon monoxide, carbon dioxide and nitrogen oxides. Therefore SCBA, full protective gear and confined-space techniques must be used when dealing with silo fires.

Explosions in agricultural silos are not the same as explosions in grain elevators. Grain elevator explosions are a result of very-dense dust environments that detonate from a spark or flame within the elevator. Explosions in agricultural silos are caused when oxygen enters a smoldering fire inside the structure and causes the carbon monoxide to explode.

Controlling fires in silos depends on the kind of silo involved. Misidentification or not accounting for modifications can and will injure and kill firefighters.

Conventional-silo fire suppression

Fires in conventional silos historically have posed little threat of explosion because the silos aren't designed to be sealed structures. Time is also in the firefighters' favor unless exposure problems to attached or proximal buildings develop.

On arrival at a conventional silo fire, the officer in charge should:

• Confirm preplan information;
• Have the operator and silo dealer respond;
• Check for and extinguish any hot embers that may have left the silo;
• Have the farmer move any livestock or machinery from the area and adjacent structures, if possible;
• Raise the silo unloader machine as far as possible via a hand crank or electrical switch at the base of the silo to minimize damage to its parts from heat and fire;
• Disconnect and lock-out and tag-out the electrical supply to the silo unloader.

Once these preliminary steps have been taken, a firefighter with full protective gear, including SCBA and a full-body harness and lifeline, should assess the fire from above the silage. If it's safe to do so, this task can be performed with a ladder truck or by climbing the silo's exterior or chute. Climbing silos should be done with caution, as the ladders and steel rungs usually are very slippery. In addition, the chute ladder may be broken or damaged by the fire. The chute also may be full of hot embers. Once above the fire, the firefighter should extinguish any visible hot spots.

A fire in a tower silo is typically located around the perimeter, the unloading doors and/or the top few feet of silage. Because a fire burning for an extended period of time can create hollowed-out cavities in the silage, any firefighter entering a burning conventional silo after knockdown of the burning surface must be secured with lifelines and stand on long boards or ladders. There are no interior ladders, per se, only the steel support rings at the chute opening. Confined-space techniques must be followed. At this point, penetrating nozzles can help to reach subsurface burning.

Using carbon dioxide or nitrogen to extinguish conventional silo fires is a questionable practice, as the structure is open to atmosphere and oxygen usually can still reach the fire. Some departments have had success with these gases, but more experimentation is needed.

It's usually impossible to completely extinguish fires in conventional silos. Even when the fire appears to have been extinguished, it sometimes re-ignites. The farmer must partially or sometimes totally empty the silo. Firefighters may have to be present during this unloading to douse hot spots. When unloading is an extended operation, consider rotating personnel and/or lending the farmer a portable pump, pond and hose. Fire officers, farmers and the farmer's insurance representative need to discuss any further actions.

Oxygen-limiting — silo fire suppression

Oxygen-limiting silos can explode when on fire, so it's imperative that firefighters know when this type is involved. An unmodified oxygen-limiting silo will not have an exterior chute.

Allowing any air to enter the carbon-monoxide — rich environment of the silo can cause an explosion. Therefore, do nothing that may cause air to be drawn into the silo. Don't attempt to open hatches or spray water or foam inside. Firefighters have been killed when they inject water and/or foam into burning oxygen-limiting silo.

Response to a fire in an oxygen-limiting silo should involve the following steps:

• Confirm preplans.
• Have the farmer and silo dealer respond.
• Do not increase the amount of oxygen inside the silo. Don't open hatches or unloader doors, and don't inject water or foam.

Firefighters should stay off a structure that is shaking, hot, noisy, smoking heavily or has been opened within the past few days. If the structure is quiet, motionless, cool and has not been opened within the past few days, and if smoke is minimal, firefighters should close the bottom unloader door and top hatches. Do not lock down these hatches, as they allow the silo to vent itself.

Inspect for extension into any adjacent-structures and have the farmer evacuate these structures if possible. If the silo walls next to combustible barn walls are hot, create a space between the two to reduce the likelihood of the silo igniting the barn.

Leave the silo closed for two or three weeks. If the structure is well sealed, the fire may self-extinguish. Regular monitoring of the silo and adjacent areas is important. If the fire continues to burn, you may have to inject carbon dioxide or nitrogen. Ask the silo dealer for assistance.

Modified-silo fire suppression

Extreme caution should be exercised when dealing with a modified solo. Fire departments that have employed incorrect suppression techniques on these structures have paid a high price in firefighter injury and death. Securing technical assistance is critical. As there are many ways silos can be modified, each case must be managed individually.

Silo fires are not common, but the possibility of firefighter death and injury is always present. Usually there's no great hurry to extinguish silo fires because they generally are well-contained by the structure. Rushing into fire suppression activities can be disastrous.

Rescue challenges

Rescues and recoveries of farmers from inside silos can be very challenging operations. Removal of a farmer can be difficult and time-consuming. The manner in which a victim is physically removed from the silo depends on four factors:

1. Patient's condition

   Is this a rescue or recovery? Is the patient's condition stable or unstable? Basically, how much time do you have to accomplish this rescue? An unstable patient will suggest a more aggressive manner of egress. A stable or non-salvageable patient dictates a less aggressive manner.

2. Expertise of rescuers on scene or through mutual aid

   In many areas rural fire-rescue companies do not have much, if any, high-angle or confined-space rescue experience. This lack of expertise reduces the number of options that departments can employ safely. Good pre-incident planning and regular practice and training on different rescue scenarios are a must. Successfully practicing rescue skills is a good predictor of how rescuers will act in real situations.

3. Availability of ladder company

   Most rural rescuers have little or no access to an aerial apparatus. For the services that can get access to such pieces, calling for them may be helpful. Extreme care must be taken if such pieces are used on farms because of the lack of a solid base for the piece to work from.

4. Conditions inside the silo

   A hazardous environment will affect the amount of time the patient can remain viable.

All these conditions need to be evaluated when deciding which form of patient egress to be employed. Limiting the number of injured or killed is an ever-present priority, requiring command officers to continually analyze the risks and benefits of operations.

Egress methods

Conventional silo rescues and recoveries can be accomplished by different methods. The following are options for removing victims who can't safely exit under their own power.

Down the chute

This method involves placing the victim into a full-body harness and lowering him or her by rope from an anchor point above. This method is arguably the easiest, safest and often the fastest to accomplish. However, not all victims can be removed by this method. Victims on backboards will obviously won't “bend” at the waist to make the turn down the chute.

Because this type of egress can be done relatively quickly, unstable victims who do not require spinal immobilization may benefit from this method. On the other hand, it's difficult to protect the victim as he or she is lowered down the chute. Also, non-salvageable patients can be taken out this way to keep rescuer risk at a minimum.

Through the chute

This manner of egress is accomplished by passing the patient on a long board out a silo unloader door and then through the exterior chute. This is a more technical rescue as it employs a rigging system and/or an aerial apparatus, making it more difficult and time-consuming.

Through the wall

This manner of egress is similar to the through-the-chute style, only the egress takes place through the wall of the silo. Breaching the wall of a conventional-silo can be easy or difficult, depending on its construction: Concrete-stave silo walls are easy to breech; whereas poured-concrete walls are much more difficult. The rigging or aerial apparatus requirements are similar to the through-the-chute method.

Out the top

Bringing the patient out the top of the silo is the most technical manner of rescue/recovery. This requires a specially trained high-angle team that has successfully practiced on silos. The patient must be secured in a stokes basket or equivalent and then raised out the top of the silo from an anchor point above the opening. The roof of the silo itself may have to be widened to accommodate this rescue. Once the stokes basket is raised out the top, it is lowered to the ground by a rigging system or taken down with the assistance of an aerial apparatus.

All of these techniques are intended for conventional-silo rescues. In fact, many people question whether rescue from an oxygen-limiting silo is even possible. Victims taken from these silos often are non-salvageable due to the oxygen-deficient and toxic-gas atmosphere. However, at least one successful rescue of a farm worker from this type of silo has occurred, but the victim was only a short distance from the silo's top hatches.

Rescue detractors say these emergencies should be treated as body recoveries, noting that several rescuers were injured in New York state in 1985 during an oxygen-limited — silo rescue. Entry into these silos for a rescue or recovery needs to be done by well-qualified, well-trained personnel. Rescuers with little or no confined-space expertise place themselves in great peril.

Emergencies involving silos present hazards that may not be obvious and can injure and kill farm workers and fire-rescue personnel. Rural rescuers need to educate themselves on local agricultural practices and prepare themselves appropriately.

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Ted Halpin is an extension support specialist for Cornell University, Ithaca, N.Y, and the co-founder of the university's FARMEDIC program, which has been training rural fire-rescue personnel in farm emergencies since 1981. Halpin grew up on his family's farm and has 24 years of volunteer and career fire, rescue and EMS experience. He holds undergraduate degrees in agriculture and fire protection and a master's degree in public administration.

Vertical Silo Hazards

The list of hazards associated with vertical silos is long and diverse. Climbing silos can be a dangerous task, and falls from heights are common. Ladders, steel rods, and hand- and footholds can be slippery, loose or broken.

High winds makes working on a silo even more difficult. In addition, a farmer or rescuer may fall into, or off of, a silo due to hidden hazards, such as electrocution or the inhalation of silo gas. Heart attacks and respiratory problems can be caused or aggravated by strenuous activity, inhalation of silo gas, allergens, fire byproducts or oxygen-deficient atmospheres.

Other upright silo hazards include fires and the explosions caused by them. Alongside the silo dangers is the silo unloader, which has many moving parts, including augers, shafts, and chains. Farmers have become injured and even entangled by these powerful machines.

Finally, the collapse of a silo can yield obvious hazards. Uneven filling, unsafe demolition, poor construction, deterioration over time and barn fires can cause the collapse of a silo. A falling silo will destroy everything in its path. A collapse zone should be considered when positioning apparatus and personnel.

Not The Average Silo

Horizontal silos include the plastic-bag type or the so-called bunker, trench or pit. Bunker, trench and pit silos are open areas with earthen or concrete walls. Silage is dumped to these silos by trucks or wagons. The silage is then compressed by driving heavy tractors over the silage, which then is covered with plastic sheeting. As the year goes on, the farmer removes just enough to feed the livestock each day. The farmer uses a bucket loader to unload the silo.

The primary hazards surrounding bunker-type silos are tractor overturns and entrapment of people by falling silage. Overturns occur during the filling and compacting of the silo. The overturns, which can occur to the side or rearward, can be fatal if the tractor doesn't have a roll-over — protective structure and the farmer fails to wear a seatbelt. Rescuers need to be proficient in tractor overturn extrication. Sometimes the silage in trenches consolidates. This can produce vertical walls of silage that can collapse and bury workers or children.

Because these silos are open to the air, hazardous gases are only a concern under the plastic cover. Farmers have little reason for going under the plastic cover. However, it is not beyond a child's inquisitive nature to hide and play anywhere on the farm.

Silage mold and dust can accumulate in these silos and become airborne during unloading. Some farmers and rescuers can have adverse reactions to these particles. Rescuers can protect themselves by wearing the appropriate, well-fitted particle mask.

The other type of horizontal silo uses large, white, tubular bags, of which the Ag-Bag is a popular example. Silage is brought from the fields and is “packaged” into these long plastic bags. Because these bags pack the silage tightly, driving on the silage to compact it is eliminated. This eliminates the risks of tractor overturn, like with trench silos. The silage wagon and bag storage packaging machinery, however, do contain many moving parts, and therefore bring the hazards of machinery entanglement with it.

Need for Advice

Fire-rescue personnel who can't differentiate between silo types or recognize modifications should solicit outside technical assistance, but they should select their sources carefully and consider getting a second opinion.

For example, a rural fire department responded to a farm for a silo fire, where firefighters found an oxygen-limiting Harvestore silo with smoke exiting from open roof hatches. The farmer had modified the silo by cutting openings and constructing unloading doors up the side of the silo.

The firefighters were aware of the hazard of directing water streams into the oxygen-limiting structure and called for technical assistance. Unfortunately, they received confusing information from a person in the silo business. He said that, because the silo now has unloading doors, it should behave like a conventional silo involved in a fire.

The fire department, believing the information is correct, placed two firefighters on the roof to direct a stream into the silo. Within a few minutes the firefighters noticed blue flames swirling in the structure. Seconds later, an explosion occurred. Sixty feet off the ground, the firefighters were nearly blown off the roof. The explosion broke bones and burned through their protective gear. The roof was nearly blown off the silo. Remarkably, both survived.

Technical information regarding silo fires should be confirmed by another source. This is a very specialized area of firefighting, and lives depend on good information.