How to identify blocked flues during chimney inspection?

Inspecting for Soot Buildup

During a chimney inspection, look for excessive soot buildup on the flue’s interior surface. This can be an indication of a blocked flue, as soot and creosote buildup are often a result of incomplete combustion due to reduced airflow. Check for buildup in areas with sharp turns or narrow sections, as these are common locations for blockages. For wood stove chimneys, inspect for soot buildup every 12 inches to identify potential issues.

Using Thermal Imaging Cameras

Thermal imaging cameras are an effective tool for identifying blocked flues. These cameras detect temperature variations and can pinpoint areas where heat is not escaping properly, indicating a potential blockage. When inspecting a chimney with a thermal imaging camera, look for temperature differences between the flue and the surrounding environment. A temperature difference of 10-20 degrees Fahrenheit can indicate a blocked flue.

Ground-Level and Roof-Level Inspections

Conduct a thorough inspection of the chimney and flue from both the roof and ground level. Look for signs of damage, such as cracks, rust, or gaps, which can cause blockages. Check the flue cap and any screen or guard at the top of the chimney for damage or debris accumulation, as these can also cause blockages. During the inspection, listen for unusual sounds, such as whistling or gurgling, which can indicate a blockage.