By John Riha

"It was awfully scary," says Cliff Whitehead of the sudden flue fire that roared up the chimney of his Des Moines house one autumn evening. "We had a regular fire going, then there was this tremendous noise. It took a moment to figure out what was going on."

"People don't always know they're having a chimney fire," notes certified chimney sweep Dan Hughes of Chimeney Cricket in Des Moines. A chimney fire doesn't always burst into flames with a thunderous bellow. "It can smolder and sizzle for an hour or more. You could be sitting around watching the football game and not even know you've got a fire," Hughes says.

Beware of Creosote Buildup
The culprit is creosote - a black or brown residue of combustion that collects on the inner surfaces of a flue liner. Creosote is highly flammable. If allowed to build up, it can catch fire, reaching temperatures of 2,500 degrees Fahrenheit. These high temperatures can crack "fireproof" brick, stone or clay flue liners, allowing heat to reach nearby wood framing members and other combustible materials.

Make sure your flue is free of creosote by inspecting your chimney once a year, preferably in late spring or early summer when heating season is over, Hughes says. That way, you'll have enough time to complete any repairs before the heating season begins in the fall.

The following are tips from Hughes on how to conduct inspections and repairs yourself or how to find a credible chimney sweep who will thoroughly clean your fireplace and chimney and check it for defects:

Do-It-Yourself Inspections and Repairs

• Wear old clothes and equip yourself with a dust mask or respirator and a pair of safety goggles.
• Check the firebox for damaged brick and mortar that is crumbling or missing. These defects usually can be repaired with refractory cement - a tough, heat-proof sealant available through fireplace dealers.
• Open the damper completely. It should move freely and fit snugly against the smoke shelf. Use a flashlight to check the damper for cracks, pitting or rusted-out sections. Broken or corroded dampers should be replaced by a professional. Look for any debris that may restrict air flow and remove it.
• Check for broken or damaged bricks or flue liners. Vertical cracking in the liner is a sure sign of a previous flue fire and should be considered a serious problem. Consult a professional chimney sweep or a masonry contractor who is familiar with fireplace repairs.
• Finally, inspect for creosote deposits. If it has built up to a thickness greater than 1/8 inch, remove it. If you can't see the entire flue from below, you'll have to get up on the roof and inspect the flue from above. Don't get up on the roof unless you are completely confident of your abilities. By attaching ridge hooks to the end of a section of ladder, you can make a safety ladder that lays flat and secure against the roof surface.

Shopping for a Chimney Sweep
To find a chimney sweep, start by looking in the Yellow Pages of your telephone directory under "Chimney Cleaning." Or contact the Chimney Safety Institute of America (CSIA) at (800) 536-0118 or visit the web site at http://www.csia.org/. You can also visit the site for the National Chimney Sweep Guild (NCSG) at http://www.ncsg.org/.

Determine professional qualifications, especially of those found in the Yellow Pages or through referrals. Chimney sweeps are not regulated or licensed by government agencies, but many sweeps apply for certification by CSIA or membership in the NCSG. These organizations promote professionalism in the industry by testing applicants and offering continuing education opportunities to keep members up to date on changing technology and fire safety.

Ask what services are provided for fees. For $90 to $150, a professional chimney sweep will thoroughly clean your fireplace and chimney and check for defects. Many sweeps lower video cameras and lights into chimneys to provide a close look at walls and liner surfaces, and to take a visual record of the chimney's condition for the homeowner.

Other key questions: Are they qualified to complete necessary repairs, and if so, what are the additional fees? If they aren't qualified, will they recommend a professional masonry contractor to do the job?

John Riha, a former building contractor, has been editor for Country Home, Traditional Home and Renovation Style magazines. He is the author of seven books about home improvement and design.