Critters in chimney could be a sign of cap damage

Q: Last night, I heard a noise coming from my fireplace, and when my husband looked, he saw a squirrel in the chimney. He also found a bird's nest, which helped to explain the fluttering noises we heard all summer. We have a chimney cap, but they still get in. What can we do?

A: The first thing would be to check the chimney cap for damage. If you have the right equipment and feel safe climbing on the roof, it would be easy to see if the protective "pest screen" covering is damaged. If the roof is too steep or if you are uncomfortable climbing on a roof, it would be best to hire a professional chimney sweep to check the flue cap.

When hiring a chimney sweep, look for one associated with the Chimney Safety Institute of America or the National Chimney Sweep Guild. As a matter of safety, you should always hire a professional when working on any part of the roof. While the chimney sweep is there, have him inspect the flue liner for signs of creosote buildup, cracks or for anything that might block the flue gases from escaping the home.

If you decide to inspect and clean the flue yourself, here is a checklist of some important items to look for:

1. Check to make sure that all of the clay tile liners are tightly sealed at their joints. Liners that are offset or have gaps between the tiles need to be repaired.

2. A dirty flue liner with a shiny coating of creosote is a fire hazard and should be cleaned by a professional chimney sweep before the fireplace or wood-burning stove is used. This type of creosote is both hard to remove and flammable, often leading to a chimney fire.

3. If the chimney is brick-lined or one without a clay tile or metal liner, it needs to be checked for blockages at the damper to the fireplace or at the chimney-cleanout opening. Over the years, the interior brick lining can fail when pieces of the brick fall to the bottom of the chimney. Over time, the debris can build up to the point where it blocks the damper, or in the case of a connected flue pipe, the pipe itself can be blocked. This is a serious situation that requires immediate repairs.

Carbon-monoxide (CO) poisoning caused by damaged or blocked flues is partially responsible for the more than 500 CO-related deaths reported in the United States each year. Carbon monoxide is a colorless, odorless and tasteless toxic gas produced by the incomplete combustion of fossil fuels. People with CO poisoning are often misdiagnosed as having flu-like symptoms. CO can cause headaches, nausea, dizziness and confusion and, if left undetected, overexposure to even small amounts of CO can be fatal. All homes — even total electric homes with attached garages — should have at least one CO detector installed.

4. Stand-alone wood-burning stoves need to be inspected for proper and safe clearances to combustible materials. According to the Maine State Fire Marshal's Office, a free-standing, wood-burning appliance should have a minimum of 36 inches on all sides of the appliance and an 18-inch clearance to the stovepipe.

5. Make sure the chimney cap is in place. The chimney cap not only protects the flue from pests, but the screening helps to control the emission of hot embers that can be a fire hazard to the roof or to other nearby combustible materials.

6. Be sure to use dry and seasoned woods in any wood-burning appliance.

Dwight Barnett is a certified master inspector with the American Society of Home Inspectors. Write to him with home-improvement questions at d.Barnett@insightbb.com. Sorry, no personal replies.