Choosing the correct size of a chimney brush is important in order to clean all sides of the chimney. The procedure to clean chimneys is based on the principle of contact on all side walls at once so that all vertical surfaces are clean from debris, animal nests and any flammable materials that can lead to a fire hazard. Clean chimneys before making the first fire of the season in a fireplace or a stove to keep harmful fumes venting outdoors correctly.
Place a ladder against the side of the house and climb it to the roof. Locate the chimney on the roof.
Use a measuring tape to measure the top of the chimney. Measure the opening on the fireplace or woodstove chimney on the inside of the opening. Measure in both directions for a horizontal size and a vertical size and record the measurements on a piece of paper with a pen.
Measure the diameter on the inside of round chimneys to choose the proper size of chimney brush. Choose a brush that is as big as the smallest measurement of the chimney so that it will touch all the walls inside at once. Chimney brushes that are 5 to 7.5 cm (2 to 3 inches) larger than the chimney opening will reach all walls.
Use a wire bristle brush for masonry chimneys. Professional brushes are a little more expensive but have a larger concentration of bristles and do a better job in a shorter amount of time.
Use a poly chimney brush for metal chimneys and older masonry chimneys. Poly bristles will not scratch metal chimneys and are gentler on older chimneys.
Chimneys are not always square. Take measurements to the nearest 3 mm (1/8 inch) to choose the correct size of chimney brush. Chimney brushes with poly bristles will not go around fixed objects inside a chimney.
If the chimney brush is more than 5 or 7.5 cm (2 to 3 inches) larger than the opening in the chimney, it will be harder to push the brush up and down to perform cleaning. Always have a second person on the ground when someone is on top of a roof. The person on the ground can call for help in the case of an accidental fall or emergency.