Fairfax County Fire and Rescue Department units responded on March 15 at 4:30 p.m. to a reported house fire in the 1900 block of Baton Drive in the Vienna area.
Arriving units found smoke showing from the exterior of the single-family home and quickly extinguished the fire. The fire was confined to the exterior of the home, with minor extension into the nearby detached garage.
There were no reported civilian or firefighter injuries, officials said.
No one was home at the time of the blaze. A passerby saw the fire and called 911. The home had working smoke alarms, but they did not activate due to the location of the fire.
Fire investigators determined that the fire was accidental in nature and started in a mulch bed. The fire was caused by spontaneous combustion of the recently added mulch, they said.
No occupants were displaced as a result of the fire, which caused about $25,000 worth of damage.
The Fairfax County Fire and Rescue Department used the incident to remind residents that mulch is an inflammable material. Mulch and wood chips are wood products that continually are decomposing, generating high temperatures.
Spontaneous combustion can happen when a decomposing material generates enough heat to ignite without an outside source. Because of this, a large enough pile of mulch or chips can create sufficient heat to spontaneously combust.
Mulch fires are more likely to start when the weather is hot and it has been dry for an extended time, officials said.