Because it’s made with sturdy material, rubber waste is a popular choice for mulching. It’s typically made of shredded recycled rubber.
Since rubber mulch doesn’t easily decompose and adheres to the ground effortlessly, it’s effective in barring floods and erosion.
Despite its enticing benefits, plenty of concerns surround rubber mulches. This includes its vulnerability to heat.
So, does rubber mulch get hot?
Upon extensive exposure to heating elements and sunlight, it’s common for rubber mulches to get hot. Find out how heat impacts their effectiveness and safety and what precautions can be taken to mitigate this recurring issue.
Understanding the chemical composition of rubber mulch is essential in determining its capacity to take up heat. First, rubber mulch is made of dye-treated rubber waste like the ones from old vehicle tires.
Vehicle tires are manufactured by combining natural rubber (from Hevea or rubber trees) and synthetic rubber polymers with other chemical additives.
Synthetic rubber composes around 60% of rubber tires since natural rubber is expensive to manufacture. These are made with hydrocarbons derived from petroleum or fossil fuels.
Therefore, rubber mulch can be prone to heating and flammability due to its carbon and petroleum origin.
According to a study, rubber mulch can reach a surface temperature of 179.42 °F during sunny days with temperatures as hot as 98.6 °F.
This means it can get even hotter under extreme thermal conditions, and it’s essential to observe safety precautions.
Aside from sunlight exposure and their innate susceptibility to heat, did you know that rubber mulch color influences heat retention, too?
Interestingly, dye-treated mulch is available in various colors like red, brown, blue, and black. I also found some light-colored ones that resemble sandstone.
That said, dark-colored ones, especially black, have higher thermal capacity, so they heat up more than light-colored rubber mulch.
Light-colored rubber mulch, on the other hand, reflects light. That’s why they don’t heat up as much.
Burning or spontaneous combustion is a common concern for rubber mulch. While it’s prone to heating, rubber mulch burning from prolonged sun exposure is unlikely. However, direct exposure to fire sources can cause rubber mulch to burn.
In addition, rubber mulch is combustible under dry, hot, and windy weather. More than 2 months of outdoor exposure increases ignitability, too.
It’s also important to note that rubber mulch can only become a significant fire hazard source at temperatures 400°F and above.
To prove this, significant findings from the University of Nevada Cooperative Extension suggest that rubber mulch is highly combustible.
It also demonstrates the most hazardous fire behavior compared to organic mulches.
When ignited, rubber mulch exhibits the highest flame (up to 3 feet), but it doesn’t spread fast. It also burned at a maximum temperature of more than 600°F.
Due to its shock-absorbing capacity, rubber mulch is commonly layered on playgrounds to limit physical injuries. However, hot rubber mulch can be a potential health risk, especially to children.
NBC News reports that rubber mulch, made from recycled vehicle tires, can release volatile organic compounds or VOCs in the air once heated.
Vehicle tires contain dangerous compounds, including heavy metals and carcinogens like benzene and mercury.
Once inhaled, these harmful substances can irritate the respiratory tract or cause nausea, with prolonged exposure resulting in organ damage and cancers.
Aside from health hazards, coming into contact with hot rubber mulch can cause burns or skin blisters. Since rubber mulch can heat up to over 170 °F, it can be dangerous to walk on, too.
Follow these tips to prevent fire hazards and reduce risks that come with using rubber mulch:
Since rubber mulch is highly combustible under favorable conditions and with the presence of an ignition source, it’s best to keep it 30 feet away from your house or other wooden structures.
If your area is prone to wildfires, it’s best to skip using rubber mulch and take extra precautions, as embers can accumulate and trigger fires.
During scorching temperatures, watering your mulch helps regulate temperatures and prevent ignition.
One of the advantages of rubber mulch is its resistance to molds that manifest due to excessive moisture. That way, you wouldn’t worry about harmful rots that can be detrimental to your plant’s health.
Be cautious with open flames, and dispose of your cigarette butts properly. You should also avoid using grills and fire pits near the rubber mulch to prevent accidental fires.
Keeping flammable substances like propane tanks at a safe distance should be done, too.
Here’s a quick summary of the rubber mulch’s advantages and downsides:
- Low maintenance
- Suppresses weed growth
- Retains moisture
- Durable and long-lasting
- Adheres firmly to the soil, preventing floods and erosion
- Resistant to molds and pests
- It doesn’t contain any nutrients
- Costly compared to organic mulches
- Contains hazardous chemicals
Here are the answers to the most common questions people also ask about rubber mulch:
Newly opened rubber mulch can smell similar to brand-new tires. It has a faint, rubber-like smell. Upon heating, rubber mulch gives off a strong, pungent smell.
I prefer installing a fabric barrier underneath my rubber mulch as it enhances weed blockage, allowing my plants to thrive without compromising the aesthetic appeal.
For landscaping or gardening, rubber mulch should be 1-2 inches in depth and not too thick to encourage air circulation.
Rubber mulch is a popular choice due to its durability and strong ground adherence. However, it can get hot and emit harmful fumes that harm one’s health.
It’s a potential fire hazard at temperatures above 400°F, too. With that in mind, rubber mulch isn’t recommended for areas prone to wildfires. At the same time, it shouldn’t be installed near foundations, with fire sources like grills at a safe distance.
Ben has a bachelor’s degree in construction engineering. When not constructing or remodeling X-Ray Rooms, Cardiovascular Labs, and Pharmacies, you can find him at home with wife and two daughters. Outside of family, He loves grilling and barbequing on his Big Green Egg and Blackstone Griddle, as well as working on projects around the house.
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