During winter you can leave some ash in the firebox from previous fires. It’s best not to let them become too deep though. If the ash layer is 2” or greater, you should remove the ash. Otherwise, the firebox should be cleaned once per week. During spring and summer when you’re less likely to use the fireplace, remove all of the ashes from previous fires. You can remove ash using a fireplace shovel and a metal bucket. Empty the bucket into the trash, or sprinkle the ash in your garden or compost pile. Next, vacuum out remaining ash and debris with a shop vacuum. Be sure that the ash has been cool for at least a couple of days before vacuuming.
Remove soot stains with soapy water and a heavy-duty sponge. For tougher stains, scrub vigorously with a stiff wire brush and muriatic acid to clean the firebox. Mix a solution of acid and water, as directed by the manufacturer’s instructions and then apply it to the stains. Let the solution sit for at least 20 minutes, and then scrub with the brush.
Muriatic acid can be hazardous to handle. Use with caution and follow all instructions on the container.
Wear gloves, safety goggles and a dust mask when cleaning out the firebox.