Any wood stove or solid fuel BBQ will have ashes that accumulate. Leaving some ashes in the wood stove helps the burning process by allowing for longer burn times and creating a warm stove in the morning (which makes it easier to restart the fire). However, ashes should be removed from a wood stove when they start blocking the lower combustion air port. A good rule of thumb is to remove two-thirds of the ashes and allow one-third to stay inside.
Cleaning ashes and disposing of them is at the bottom of the task list for most people. This means that the people who find the time to complete this task often haven’t been trained to do it safely. Perhaps that’s why ashes or embers cause 6% of residential house fires. This can be rephrased as “the improper disposal of ashes.” Insurance companies study these statistics, so it’s no surprise that they often increase rates for customers with solid fuel appliances. What’s more, the dangers posed by ashes have led many housing communities to ban wood stoves and solid fuel BBQs altogether.
Why are ashes such an issue? Because they’re misunderstood. Simply put, ashes are the minerals remaining after the combustion process. As such, they are the 1%-2% of the solid fuel that is not combustible. The ashes form a fluffy matrix that insulates embers and allows air to infiltrate slowly. As a result, small embers and unburned fuel can sit in this comfortable matrix for days. Fire investigators often use the 72-hour rule to consider ashes placed in a cardboard box or paper bag as a potential ignition source.
So, we know that ashes can contain embers, and we also know that these embers can hide comfortably in ashes for days. Given these facts, how can we safely dispose of ashes?
The answer is simple: Use a steel bucket, fill it two-thirds full with ashes, and take it outside. Then, fill the bucket with water above the level of the ashes, place it in an area away from structures, and wait for three days. Finally, move the ashes to a garden or the trash can.