The Hidden Fire Hazard in Your Backyard: How Lawn Mowers Spark Wildfires
- Fire Roots
- Jun 30
- 3 min read
Updated: Jul 11
Fires can be devastating for homeowners; people can lose all they have within a burning blaze. Yet at the same time, most fires are easily preventable and are often the result of homeowners simply being unaware certain seemingly safe actions can lead to fires. One such unexpectedly dangerous action is lawn mowing. Across California alone, fire crews respond to over 1600 cases of fire caused by lawnmowers. When used improperly, even commonplace items can lead to disaster for homes and people.
The primary danger that stems from these lawnmowers are the interactions between a lawnmower’s blades and hidden rocks. When high speed lawn mower blades spinning at over 2800 rotations per minute hit rocks hidden within lawns, the immense speed of the blades generate extreme amounts of friction and heat, causing sparks to fly all over the place, often at temperatures of thousands of degrees. Though these sparks are normally harmless to humans because of how small they are, when they fly into piles of dry grass, it has a chance of completing the fuel – oxygen – heat triangle necessary to start a fire.
Another fire risk comes from improperly maintained lawnmowers. Sometimes, plant debris can be stuck on lawnmower exhaust pipes after use. If the lawnmower is not properly cleaned afterwards, the plants on the exhaust pipes could block cooling. The trapped heat is then forced to transfer into the plant matter instead of air, which could lead to combustion. As Paul from Jr Small Engine Repairs puts it, “5 minutes is all it takes” to set the trapped plants ablaze.
Fires caused by lawn mowers are not only dangerous but can also carry severe legal and financial consequences. According to Rick Carhart, an information officer serving under Butte County Fire department, individuals can be held liable for fires that’s started by negligence. In addition, most homeowners insurance typically does not cover fires caused by overlooking fire hazards. The potential consequences stemming from this makes it all the more important for homeowners to be extra careful when it comes to understanding how to safely use their lawn mowing equipment.
Thankfully, the dangers from lawnmowers can be fully mitigated if used correctly. The North Sonoma County Fire Protection district provided helpful advice on mitigating risk. Landowners should only use lawnmowers in the early morning before 10 AM, when the air is cooler and more humid. In addition, mowing should be avoided entirely if the grass is dry, if temperatures are above 90 degrees Fahrenheit, or if the relative humidity is below 30%. Never use a lawnmower on dry grass directly, instead, opt for a weed trimmer, which uses a spinning nylon or plastic lines to cut grass instead of metal blades, drastically reducing the chance of creating sparks from hitting rocks.
Another important aspect of reducing fire risk is maintenance. Scott DeNoon, a member of the Virginia Farm Bureau’s Safety Advisory Committee, advises homeowners to do a variety of maintenance actions before and after mowing. Oil levels should be checked between each use, but they should never be refueled when the machine is still hot. Instead, refuel before mowing, or after the machine has fully cooled down. After each mowing session, clean out the grass from mower blades and exhaust pipes with a hose before storing, to prevent the aforementioned buildup of plant debris. Regularly sharpen the blades on the lawnmowers; dull blades are not only less efficient at cutting grass, but also more likely to create sparks, due to needing more pressure to cut effectively. Finally, it’s also critical to inspect the mower for any fuel leaks and to clear the mowing area of rocks and other hard debris beforehand.
While lawnmowers are a routine part of lawn maintenance for homeowners, they carry serious hidden fire risks that can have devastating consequences. From sparks caused by blades and rocks to heat buildup on exhaust pipes, lawn mowers provide a very dangerous potential of ignition. Yet, through proper usage, awareness of dangers, and proper maintenance, the dangers caused by lawnmowers can be entirely contained, allowing individuals to protect not only their own property but also their community from potential catastrophes.
-Written by Luke Song
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