There isn’t a simple rule of thumb on how often to clean your chimney, such as cleaning after 50 uses or one year. The problem is, creosote can form when wood is burned incompletely. In addition, organic, flammable debris can enter the chimney, brought by the elements or by animals. Wind can deposit leaves and twigs in chimneys lacking flue caps. Birds and vermin can nest in chimneys or otherwise bring unwanted materials. A smoky fire without enough oxygen emits lots of unburned tar vapors that can condense inside the fireplace flue and stick to it, possibly leading to a chimney fire. You can reduce creosote buildup in your fireplace flue by providing adequate combustion air, which will encourage a hot, clean-burning fire.
Chimney fires begin with snaps and pops as loud as gunshots, progressing to a deep, rumbling sound. Oily, black, flaming creosote rains down into the firebox. When the fire starts, it starts like an explosion. Flames blast out of the top of the chimney and back down into the firebox. Due to thermal expansion, the flue may crack at some unreachable mid-point and shoot flames into the walls from the inside. Chimney fires typically cannot be controlled by the homeowner. Since firefighters have to shoot water from the top downward, the house suffers damage from flooding. In many cases, the entire house is lost.
Chimneys should be cleaned no later than the early fall, prior to fire burning season. If you choose to hire a chimney sweep, you can expect a quick turnaround if you have them come earlier, ideally in the late spring or summer. For self-cleaning, late summer is the best time, since you can count on a dry, safe roof and mild conditions.
In addition to scheduled chimney cleanings, you should clean when any of these conditions are present:
Soot and creosote tend to fall into the firebox during a fire
Honeycomb textured creosote builds up on the inside of the chimney
Creosote is more than 1/4-inch thick
You burn a lot of artificial logs
You are a heavy fireplace user
You burn green or otherwise unseasoned firewood
How to Check for Creosote
To check for creosote, shine the light near the top of the firebox, in the smoke chamber and around the damper. And check the fireplace flue, too, especially on exterior chimneys, where creosote builds faster than on interior chimneys because of lower outside temperatures. The easiest creosote to remove is the feather-light dull gray, brown or black soot. The next form is a black granular accumulation, removed fairly easily with a stiff chimney brush.
The third type of creosote is a road tar-like coating that is much harder to remove even with stiff chimney brushes, scrapers or power rotary whips. The final (and most deadly) is a shiny, glaze-like coating on the fireplace flue that is virtually impossible to remove.
In case you didn't know, we have a highly qualified chimney sweep on staff at Sunpoke! Darren does a very professional and detailed cleaning. He is also WETT Certified, so is able to do Inspections at the same time.