Is hay flammable?

This blog post will answer the question, “Is hay flammable” and cover topics like the flammability of hay, and frequently asked questions related to the topic.

Is hay flammable?

Yes, hay is flammable. When the internal temperature of hay reaches over 130°F (55°C), a chemical reaction occurs, producing flammable gas, which may burn if the temperature gets high enough. Hay that is loose, in little or big bundles or stacks, and kept indoors or outdoors might catch fire.

How to reduce hay fire?

To reduce the danger of hay fires, do the following steps:

  • Check your regular basis. If you notice a faint caramel flavor or a pronounced musty stench, your hay is likely to be heating. It’s too late to assess the moisture at this time; you’ll need to keep an eye on the hay’s temp.
  • Insert a simple sensor into the haystack to measure the temperature if you fear your hay is heating. A probe may be made out of a 10-foot length of pipe or electric tubing. Drill multiple 1/4-inch-diameter openings in the tube slightly above the dowel after sharpening one end of the tube or screwing a pointed dowel to one end. Lower a thermometer on a thread into the probe and drive it into the haystack. Place the probe in various places of the stack and leave it there for ten min at each location.
  • Place large boards on top of the hay before examining the tops of stacks. Do not go across the haystack. Always wear a safety line around your neck and have someone on the other end in a safe area to pull you out if the hay surface collapses into a fire pocket.
  • At roughly 240 degrees Fahrenheit, hay treated with preservatives like ethoxyquin and butylated hydroxytoluene produces hydrogen cyanide gas (115 C). When battling a fire in this hay, exercise extra care since this gas is toxic.

Preventing Spontaneous Combustion of Hay

When the core temperature of hay exceeds 130 degrees F (55 degrees Celsius), a chemical reaction occurs, resulting in flammable vapors that may ignite. The majority of hay fires happen within six weeks following baling. Heating occurs in all hay over 15percentage moisture content, although it typically peaks at 125 to 130 ℉ in three to seven days, with little danger of burning or forage quality loss. The interior temperature will drop to a safe level in the following 15 to 60 days, depending on stack density, external temps, moisture, and rainfall.

As with other bales, it’s important to keep an eye on the temperature:

  • Check the temperature regularly at 150 degrees.
  • At 160 degrees, check the stacks every 4 hours and monitor the temperature.
  • When the temperature reaches 175 degrees, damp the hay down, remove it from the barn or disassemble the stack away from other bales and structures, and call the fire department.
  • Hot patches or pockets are possible at 185 degrees. Most likely, flames will erupt.
  • Hay will very probably ignite at 212 degrees — this is crucial.

Take precautions and play it safe:

  • Small, square bales must not exceed 18 to 22 percent moisture for safe storage, whereas big circular or rectangular bundles must not exceed 16 to 18 percent moisture.
  • Check for new hay on a daily basis. If there is a noticeable musty odor or a mild caramel odor, the hay is most likely heating; keep an eye on the temperature.
  • Place large boards on top of the hay before entering a barn. Always wear a cord around your waist and then have another person at a safe distance on the other end to pull you out if the hay surface collapses into a fire pocket.
  • Know the feed’s composition — preservative-treated hay might be a deadly combo.
  • By removing oxygen from the hay mass, dry ice, liquid nitrogen, or carbon dioxide gas may be poured into the hay to avoid burning. Farmers used to sprinkle salt on damp hay to keep it from spoiling, but this will not stop spontaneous combustion.
  • Good storing procedures will reduce the risk of spontaneous combustion and improve the quality of the hay.

Fires in Baled Hay or Straw: What Causes Them?

The key component that causes hay and grass to spontaneously fire is moisture content. Hay fires are more prevalent than straw fires for a variety of reasons, including forage type, the moisture content in stored hay, and heat generation.

Plant fiber respiration (the burning of plant sugars to create energy) continues in plant cells after forages are cut, resulting in the emission of a tiny quantity of heat. Plant respiration slows and finally stops when forages are harvested, field dried, and baled at the appropriate moisture level (20 percent or less).

The proper habitat for the development and proliferation of mesophilic (warm temperature) bacteria prevalent in forage crops is supplied when forages are baled at humidity levels higher than 20%. Mesophilic bacteria produce heat inside the bale, causing the internal temperature to increase to between 130 and 140 degrees Fahrenheit. Bacteria die at this temperature, and the temperature of the hay drops. 

Because the inner temperature of a hay bale does not fall after the first heating cycle, it poses a larger fire danger than straw. The mesophilic bacterium’s respiratory heat offers a breeding habitat for thermophilic (heat-loving) bacteria. In general, the greater the moisture content of a bale, the longer it will stay at a high temp. A bale with 30percentage moisture content, for example, may have a higher internal bale temp for up to 40 days. The presence of thermophilic bacteria causes them to proliferate and create heat, raising the interior bale temp to above 170°F. Spontaneous combustion can occur at these temperatures.

The amount of the hay or bale stack, bale weight, and ventilation or air movement around the piled bales are all elements that contribute to the danger of hay fires. Overheating is less likely in bales with a lower density, which is stacked lower and have sufficient air movement and ventilation.

How to reduce the risk of fire?

Because microbial activity reduces at this moisture level, baling hay with a moisture content of 20percent or less is the greatest strategy to lessen the danger of a hay fire. Moisture content in baled hay may be reduced in several ways:

  • Baling in the right conditions: The weather has a big part to play in getting the right humidity content in baled hay. A moderate breeze and moisture levels of 50 percent or less are ideal for haymaking. Because hay has a greater water content in the morning, baling it later in the day is advised. Mowing hay in the morning and allowing it to dry on the field for at least one full day before baling is the recommended method for haymaking.
  • Using specialist equipment: Using specialized haying equipment intended to boost drying rates is another technique to reduce moisture content. Tedders, hay rakes, and conditioning equipment are examples of this kind of equipment.
  • Using hay preservatives: When applied to hay during baling, hay preservatives such as liquid propionic acid block or limit the development of microorganisms in the hay with high water content.
  • Another strategy to lessen the danger of a hay fire is to keep the hay dry while it’s being kept.
  • If you’re keeping hay indoors, ensure sure the barn or storage room is weathertight and has enough drainage to keep water out.
  • Cover hay with plastic or another form of waterproof covering before storing it outdoors. If you can’t cover the bales, position them so that air may travel between them to speed up the drying process. By placing bales on a bed of gravel or elevating them off the ground on old tires, poles, or pallets, they may be protected from ground dampness.

Hazards of Hay Fires

Hay fires pose the following three dangers:

  • Flare-Ups: If the inside hay bale temp is between 150°F and 170°F, the hay must be relocated to let it cool. Moving the hay might expose it to oxygen and trigger flare-ups if the temp is at the upper end of the range. Make arrangements with your local fire station to have charged water hoses on hand.
  • Burned-Out Cavities: When temperatures deep inside stored hay reach high temperatures and the hay burns, these cavities occur. If a person walks over the top of the hay pile, he or she may get stuck in a burned-out cavity. A haymow should be investigated by at least two individuals due to the possibility of falling into a burned-out cavity.
  • Toxic Gas: Smoldering and burning hay may generate toxic gases such as carbon monoxide. Toxic gas fumes may be released from chemically treated hay. In either case, a qualified firefighter with self-contained breathing equipment (SCBA) should be sent to the site.

Important things to remember regarding hay fire

  • The majority of hay fires caused by moisture levels happen during the first 6 weeks after baling.
  • Maintain a moisture level of 20% or less while baling hay.
  • Cover baled hay or store it indoors to keep it dry.
  • Regularly check the temperature of the inside bale.
  • The responsibility of monitoring hay temperatures should not be assigned to youth employees.
  • If you’re storing uncovered bales outdoors, make sure they’re arranged in a way that allows air to flow around them.
  • The amount of ventilation used varies according to the temp of the hay. Increased airflow around the bales will assist the hay recovery to an appropriate temperature at lower temperatures. If the temperature of the hay reaches 175 degrees Fahrenheit, cease ventilating it because the increased airflow might start a fire.
  • Maintain MSDSs for any crop preservatives that may have been applied on the hay, and make sure that fire department personnel have access to them.

Frequently Asked Questions(FAQs), “Is hay flammable?”

Are hay bales flammable?

When the internal temperature of hay reaches over 130°F (55°C), a chemical reaction occurs, producing flammable gas, which may burn if the temperature gets high enough. Hay that is loose, in little or big bundles or stacks, and kept indoors or outdoors might catch fire.

Why do farmers burn hay?

Agricultural burning aids farmers in removing agricultural wastes such as hay and rice that remain in the field after harvesting. Agricultural burning is frequently used by farmers to remove orchard and vineyard prunings and trees. Burning also aids in the removal of weeds, the prevention of illness, and the control of pests.

Is burning hay toxic?

Toxic fumes may be released by smoldering and burning hay. Carbon monoxide may build up in the smoldering fire and its surroundings. Toxic gas vapors may be produced by chemically maintained hay crops. Gases that may kill add to the danger of a fire.

How do you stop a hay fire?

Another strategy to lessen the danger of a hay fire is to keep the hay dry while it’s being kept.

  • If you’re keeping hay indoors, make sure the shed or storage room is weathertight and has enough drainage to keep water out.
  • Cover hay with plastic or some other form of waterproof covering before storing it outdoors.

How do hay bales explode?

The hay is deemed dry when it has a moisture content of 20% or less. Mold, on the other hand, will continue to develop and create heat until that moment. The heat, along with the hay’s natural oxygen content, causes the hay to burn.

How long does hay take to combust?

“Excessive heating and molding may occur depending on forage moisture during baling and how hay is kept,” Bushong added. “Depending on the circumstances, the time it takes from warming to combustion may range from a few days to ten weeks.”


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