N
The Daily Insight

Why do haystacks spontaneously combust

Author

David Perry

Updated on April 18, 2026

Spontaneous combustion inside haystacks is when moisture builds up inside a bale. That moisture starts to heat up and the oxygen inside the hay combines with it and causes a slow burn that eventually destroys the entire stack.

Why do haystacks catch fire?

Actually, wet hay is more likely to lead to spontaneous combustion than dry hay. … When the internal temperature of hay rises above 130 degrees Fahrenheit (55 degrees C) it provokes a chemical reaction producing flammable gases that can ignite. Most hay fires occur within 6-weeks of baling.

What is the point of spontaneous combustion?

Spontaneous combustion is the phenomenon in which a hydrocarbon (or a chemical substance) substance unexpectedly bursts into flame without apparent cause. In ordinary combustion, the hydrocarbon is deliberately heated to its ignition point to make it burn.

How do you keep hay from catching fire?

  1. When storing hay inside, make sure the barn or storage area is weathertight and has proper drainage to prevent water from entering the barn.
  2. When storing hay outside, cover the hay with plastic or another type of waterproof material.

What happens if hay bales get wet?

Wet bales are at risk for combustion, store appropriately and check temperatures. Anything above 170°F is high risk. Mold may produce mycotoxins, so roll out and let animals select good portions of moldy bales. Make sure other clean feed is available.

What happens if you bale hay too early?

Hay that is cut and baled with high moisture is at risk for spontaneous combustion for up to three weeks as the plant cells are still respiring. … Most fires occur within the first six weeks after baling.

Can humans spontaneously combust?

The answer is almost certainly no. None of the proposed scientific explanations for how a body would spontaneously burst into flames have held up to scrutiny.

Why do hay bales sit in fields?

If they are scattered around the field the farmer is just waiting for a convenient time to pick them up and move them. If lined up along the edge of the field they are being stored there. Big round bales can handle being left outside, and even if the outside looks weathered the inside will be good for a year or longer.

Are hay bales a fire risk?

A chemical process that releases heat can cause hay bales to spontaneously combust, sometimes leading to farm fires. … Fires caused by spontaneous combustion typically start within six weeks of hay baling and are most likely to happen when moisture levels in the hay exceed 20 percent.

Is burning hay toxic?

Smoldering and burning hay can be the source of toxic gases. Carbon monoxide can be concentrated within the smoldering fire and surrounding area. Chemically preserved hay crops may produce toxic gas vapors. Deadly gases add to the fire risk.

Article first time published on

How many people have survived spontaneous human combustion?

Frank Baker, who served in the US Army in Vietnam, is the only known survivor of the unexplained phenomenon known as spontaneous human combustion. The highly-decorated former soldier had been preparing to go on a fishing trip with his friend Pete Willey when fire suddenly engulfed his body.

Can you start a fire without a spark?

There is a real challenge to start a fire without a spark. Each spark has the potential to start the fire, yet many fail to set the flame. … The task is difficult, may seem impossible, but when faced with darkness and cold, determination is essential.

How spicy is spontaneous combustion?

The scoville units for Spontaneous Combustion Hot Sauce are about 400,000 to 500,000.

Is it OK to cut hay in the rain?

When plants are cut for hay, they do not immediately die. As long as moisture is above 40 percent, they will continue to respire – exchange oxygen and carbon dioxide – a process that burns energy. … Sometimes, rain will not reduce hay quality significantly if the hay has adequate time to dry and cure prior to baling.

What do you do if it rains on cut hay?

The trick is to get it dry again as quickly as possible in order to reduce the amount of time for leaching of nutrients. Just remember that excessive tedding or raking of hay will result in material loss so be as efficient as possible. Unfortunately, in some cases the hay will not be salvageable.

What is the white stuff on hay?

A principal concern for cattle is the total amount of mycelium and spores combined or the total “fungal biomass.” In hay, the white mold in the bale is the mycelium and dustiness is from the tiny spores.

Which part of body does not burn in fire?

The bones of the body do not burn in fire. Why do the bones not burn in fire? For the burning of bone, a very high temperature of 1292 degrees Fahrenheit is required. At this temperature also, the calcium phosphate from which the bones are made will not entirely turn into ash.

Who was the last to spontaneously combust?

The most recent death linked to SHC was that of Michael Faherty, 76, who died at his home in Galway, Ireland in December 2010.

Are humans flammable?

The human body isn’t especially flammable, she reasons, and has high water content. … That’s why it takes flames of around 1600 degrees Fahrenheit over two hours or more to cremate human remains. A cigarette tip, in contrast, only burns at around 700 degrees Celsius.

How long can hay bales sit in field?

Hay baled with more than 22 percent moisture should probably not be put into storage for at least 30 days. This is especially true if bales are to be stacked several layers deep. With the threat of barn fires removed by outside hay storage, many operators of large round balers try to bale hay with too much moisture.

Why does hay get hot in the middle?

Spontaneous combustion occurs when moist hay heats up due to a combination of natural microbial and chemical reactions. If enough air (oxygen) is present the moist hay may get hot enough to ignite, with fire then spreading through the stack or shed.

How hot is too hot for hay bales?

Temperature 160 degrees F — Reaching the danger zone. Temperature should be checked every two hours. If possible, stacked hay should be disassembled to allow more air to move around heated bales for cooling. Temperature 175 degrees F — Hot spots or fire pockets are likely.

Can a bail of hay spontaneously combust?

Plant reactions and bacterial growth combine to raise temperatures in even the driest hay bales, although most never catch fire on their own. However, when hay is packed tightly, and enough moisture gets in, the conditions may be right for spontaneous hay combustion.

Can you stack wet hay bales?

Never stack round bales during the rainy season unless they are covered or unless they will be fed very soon. And avoid placing bales in a row with the twine or wrapped ends touching one another.”

Do hay bales go bad?

With too little moisture, hay becomes brittle, loses nutritional value, and is unpalatable for livestock. With too much moisture, hay can spoil while baled hay can experience thermal expansion—causing it to combust and creating a severe hazard.

Why do farmers wrap hay in plastic?

Most farmers seem to have their preference on moisture levels. … Bales at lower moisture may have little to no fermentation, but wrapping protects them from spoiling. On the other hand, moisture levels too high can cause clostridial fermentation with resulting high levels of butyric acid and ammonia.

Why do farmers stack hay?

The size and shape made it possible for people to pick bales up, stack them on a vehicle for transport to a storage area, then build a haystack by hand. To ease labor and increase safety, loaders and stackers were developed to mechanise the transport of small bales from the field to the haystack.

What are those big rolls of hay called?

Balers that produce the large round bales you see dotting the countryside are the most common type of balers available today. These balers produce what are referred to as ton bales. These bales of hay can weigh up to 1,500 pounds.

What moisture will hay heat?

Heating in bales occurs to some extent unless the feed contains less than 15% moisture.

Is loose straw flammable?

It may seem like a house insulated with straw poses a significant fire hazard. Yes, loose straw is indeed highly flammable. Yet, EcoCocon straw wall panels provide excellent fire resistance that is comparable to or even higher than other construction materials.

How hot is a fire?

Deep red fire is about 600-800° Celsius (1112-1800° Fahrenheit), orange-yellow is around 1100° Celsius (2012° Fahrenheit), and a white flame is hotter still, ranging from 1300-1500 Celsius (2400-2700° Fahrenheit). A blue flame is the hottest one of all, ranging from 1400-1650° Celsius (2600-3000° Fahrenheit).