How often should I have my chimney swept?
This a tougher question than it sounds. The simple answer is: The National Fire Protection Association Standard 211 says,
Chimneys, fireplaces, and vents shall be inspected at least once a year for soundness, freedom from deposits, and correct clearances. Cleaning, maintenance, and repairs shall be done if necessary. This is the national safety standard and is the correct way to approach the problem. It takes into account the fact that even if you don't use your chimney much, animals may build nests in the flue or there may be other types of deterioration that could make the chimney unsafe to use.
The Chimney Safety Institute of America recommends that open masonry fireplaces should be swept at 1/8 of an inch of sooty buildup, and sooner if there is any glaze present in the system. This is considered to be enough fuel buildup to cause a chimney fire capable of damaging the chimney or spreading to the home. Factory-built fireplaces should be swept when any appreciable buildup occurs. The logic is that the deposit is quite acidic and can shorten the life of the fireplace.
The problem is, creosote can form when wood is burned incompletely. A smoky fire without enough oxygen emits lots of unburned tar vapors that can condense inside the flue and stick to it, possibly leading to a chimney fire. You can reduce creosote buildup in your fireplace by providing adequate combustion air, which will encourage a hot, clean-burning fire.
To check for creosote yourself, first, make sure there's no downdraft from the chimney. If you feel an airflow, open a door or window on the same floor as the fireplace until the downdraft stops or reverses and air flows up (tape tissue to the fireplace opening and watch its movement). Then, while wearing goggles and a basic disposable dust mask, take a strong flashlight and your fireplace poker and scratch the black surface above the damper (smoke chamber). If the groove you scratch in the creosote is paper thin, no cleaning is needed. If it's 1/8 in. thick, schedule a cleaning soon. If you have 1/4 of an inch of creosote, do not use the fireplace again until it is cleaned-a chimney fire could occur at any time.
To check for creosote, shine the light near the top of the firebox, in the smoke chamber and around the damper. And check the 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 flue that is virtually impossible to remove.
You could try to remove creosote yourself, but for a thorough job, call a certified chimney sweep. Make sure the sweep you hire ($150 to $200) does more than push a brush. A chimney sweep needs to be knowledgeable about building codes, trained to recognize deterioration or venting problems and able to advise you regarding the chimney's condition. And the National Fire Protection Association recommends that chimneys, fireplaces, and vents be inspected at least once per year.
Save money and avoid a long wait by having your chimney inspected and cleaned in the spring.
Pulled from the Do It Yourself (DIY) experts of The Family Handyman Magazine and Chimney Safety Institute of America
County Fire Prevention Officer
Sublette County Unified Fire
P.O. Box 2410 / 130 South Fremont
Pinedale, WY. 82941