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Can Mulch Catch Fire? (A Guide to Mulch Combustibility)

Can Mulch Catch Fire? (A Guide to Mulch Combustibility)

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Numerous posts about mulch fires have circulated on social media in recent years. This leaves a lot of people questioning: Can mulch really catch fire?

Sadly, the answer is yes. Most mulch types are combustible and can catch on fire on their own or when they touch any burning materials.

However, the probability of mulch combustion differs from one location to another depending on the area’s climate.

What causes these catastrophic accidents? I’ve written this post to provide you with the answer to this question.

More importantly, I’ll provide you with the safety measures you can take to prevent any potential mulch fire.

Why Does Mulch Catch on Fire?

There are two common scenarios in which mulch fires occur.

The first is when a thick layer of mulch, 6 inches or more, is exposed to extremely high heat for an extended period.

In this case, heat builds up within the mulch pile, leading to smoldering that eventually turns into a fire.

Multiple studies support the possibility of spontaneous combustion of mulch under certain conditions, including high heat.

The second scenario for such fires is when someone disposes of flammable material, such as cigarettes, on mulch.

Mulch won’t quickly burst into flame once it touches a cigarette. Still, the smoldering of the cigarette or other flammable material can invisibly creep underneath the mulch.

Then, this smoldering will gradually develop to end up igniting the mulch after a while.

In both cases, mulch’s dryness level plays a vital role in igniting the fire. The drier the mulch is, the higher the probability of developing a flame.

At What Temperature Does Mulch Catch Fire?

Some sources state that spontaneous combustion in organic materials like mulch usually initiates when it reaches a temperature of around 300°F to 400°F.

However, the temperature at which the mulch combusts can vary depending on multiple factors, such as wind level and the dryness of the material.

Which Mulch Is the Most Fire-Resistant?

Different types of mulch vary in their combustibility. Some are highly flammable. Others are fire-resistant or even non-combustible.

Here are three mulch types categorized according to their flammability levels:

Non-Flammable Mulch

Most inorganic mulch types are highly fire-resistant. So, you can place them beside your home without worrying about fire risk.

The following are the most common non-flammable inorganic mulch types:

  • Gravel
  • Decomposed granite
  • Rocks
  • Stones
  • Brick chips

The Least Flammable Mulch Types

Some organic mulch has a low probability of catching fire. Here’s a list of these types:

  • Tahoe chips with a depth of 2-3 inches
  • Tahoe chips in a single layer
  • Fire retardant-coated Tahoe chips
  • Composted wood chips

The Most Flammable Mulch Types

Here’s a list of the most combustible mulch types:

  • Pine needles
  • Pine bark nuggets
  • Shredded rubber
  • Shredded Western red cedar

How Do You Keep Mulch from Catching Fire?

Mulch fires can be catastrophic. Nevertheless, you can avoid this occurrence with some simple preventive measures.

Here are these safety measures:

Keep Mulch as Far Away as Possible from the House

Place mulch 18 inches away from the house, grills, decks, and other structures around your home. This is to eliminate the chance of fire spreading in case of mulch combustion.

Moisten Your Mulch Regularly

Dryness increases the likelihood of starting a fire in mulch. So, you need to moisten your mulch on a regular basis to prevent it from turning dry.

This is especially crucial if you live in dry, windy, and humid areas like California.

That’s because such places are more susceptible to various types of fires, from wildfires to grass and mulch fires.

Surround Your House with Non-Combustible Mulch

To decrease the chance of fire spreading to your home in case of mulch combustion, place non-combustible mulch right next to your home.

To achieve this, use inorganic mulch consisting of sand, stones, gravel, and rocks.

Non-flammable mulch will serve as a barrier to prevent any potential fire from easily reaching your home.

Avoid Disposing of Cigarettes in Mulch

Throwing away a cigarette on mulch is one of the most common reasons for mulch fires. To avoid this hazard, dispose of your cigarettes or any burning material away from mulch.

Keep Your Garden Grass Always Short

The wide surface area of long grass can increase flame speed and allow it to spread extensively in the case of fires.

Conversely, short grass can slow the fire spread because of its small surface. That way, you need to keep the grass around your home short.

Can You Use Mulch Around a Fire Pit?

Yes, you can use mulch around a fire pit. Still, you have to keep the two objects at a safe distance of at least 10 feet from each other.

Plus, you should apply a few safety measures to ensure the fire pit and mulch won’t risk your life or property.

Here are a bunch of the most effective tips to follow:

  • Place the fire pit at least 10 feet away from the house, decks, and trees.
  • Choose a fire pit made of concrete, stone, or bricks, as these materials are considerably fire-resistant. That way, selecting any of them will lower the chance of mulch fires.
  • Build a metal ring around the fire pit to reduce the probability of embers escaping the pit, causing flames.
  • Place a fire extinguisher close to the pit to ensure you’ll be able to control any unexpected fire as soon as it arises.

Final Thoughts

Can mulch catch fire? It’s possible for mulch to catch fire, yet this accident is relatively rare.

Mulch combustion can occur when mulch is exposed to extremely high heat from the sun or any surrounding object.

This incident can also occur as a result of improper disposal of burning material like cigarettes on mulch. In either case, if the mulch is dry, the probability of fire igniting increases dramatically.

Nonetheless, taking some preventive measures can help you avoid this catastrophic occurrence.

These measures include keeping any flammable mulch away from your house as much as possible.

Moistening your mulch regularly and keeping your garden grass short can also help avoid this danger.

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