A mulch fire often begins as deep, subsurface smoldering, producing little visible flame initially. This slow, incomplete combustion allows the fire to tunnel and spread beneath the surface before erupting into open flame. These fires can smolder undetected for hours or days, allowing them to spread to nearby structures like wood siding, decks, or fences. Even a seemingly small, smoking area in a landscape bed can quickly grow and cause significant damage.
Assess the Situation and Ensure Safety
Before attempting suppression, assess the situation to ensure personal safety and the protection of property. If the fire is large, spreading quickly, or located near a combustible structure such as a house, deck, or shed, immediately call 911 or your local fire department. Professional help is required when the fire is beyond the capacity of a garden hose and shovel.
If the fire is small and contained, wear appropriate personal protective equipment before approaching. Sturdy, closed-toe work boots and leather work gloves protect your hands and feet from heat and sharp objects. Always maintain a clear escape route and position yourself upwind to avoid inhaling smoke and hot ash.
Initial Response for Surface Flames
When a small fire is discovered, the first step is to knock down any visible flames on the surface of the mulch bed. Use a standard garden hose to apply water, setting the nozzle to a focused, straight stream rather than a wide mist or spray. This concentrated stream delivers water directly to the burning material, cooling the flames quickly.
Direct the water stream at the base of the visible fire, covering the entire burning area. While this action suppresses the initial flames, surface wetting alone will not extinguish a true mulch fire. The deep-seated nature of this combustion means the fire is likely still smoldering beneath the wet top layer.
Saturating and Breaking Up Deep Smoldering
The hazard of a mulch fire lies in the deep, subsurface smoldering, which requires a complete saturation and physical breakdown of the material to extinguish. Water applied to the surface often runs off quickly, failing to penetrate the dense, dry material where combustion is actually occurring. To effectively put out the fire, thoroughly soak the entire visible area and the surrounding perimeter, extending at least two feet out from the initial hot spot.
After the initial soaking, use a shovel, rake, or pitchfork to physically turn over the wet mulch bed, breaking up the material and exposing the dry, smoldering core underneath. This aeration is necessary because the fire is starved of oxygen on the surface. Immediately apply more water to the newly exposed material until the entire turned area is completely saturated and cool to the touch. Repeat this process of soaking and turning multiple times until no heat, smoke, or red embers are visible anywhere in the disturbed mulch.
Post-Extinction Monitoring and Future Prevention
Post-Extinction Monitoring
Once you believe the fire is out, it is important to monitor the area for residual heat that could indicate a re-ignition risk. Use the back of your hand to feel the ground and the saturated mulch for any remaining warmth, checking the area every few hours for at least 24 hours afterward. If any smoke or heat reappears, immediately repeat the process of soaking and turning the material until it is completely cool.
Future Prevention
Future prevention involves reducing the risk factors that contribute to mulch fires, such as improper disposal of smoking materials, which is a leading cause of ignition. Maintain a minimum clearance of 18 inches between the edge of the mulch bed and any combustible building materials, including wood siding, decks, or fences. Avoid piling mulch too deeply, as layers thicker than two to four inches can trap heat and increase the risk of spontaneous combustion.