Before sizing your chimney make sure your fireplace and chimney are cold with no hot ash in the fireplace. Sweeping and vacuuming your fireplace will help make it easier. If you chimney has a damper you should see a metal flap with a lever that closes the chimney.
Chimneys with a damper
The Chimney Pillow should be installed, generally above the damper. Select an area for its installation making sure that this does not interfere with the damper flap or any damper hardware. The area must have parallel or slightly sloping walls ideally with texture for the pillow to grab and lodge when inflated. The damper ledge acts to provide extra support to the weight of the pillow. A Chimney Pillow can also be installed well above the damper, so it is possible to close the damper below it.
Measure the length and depth of the chimney in the location you have selected to install the pillow. Write down the dimensions, and also note if your chimney is round, circular or rectangular in the location you are measuring.
Chimneys without a damper (a chimney with no closing mechanism)
Identify the narrowest part of your chimney within arms reach. Choose an area to install the Chimney Pillow. Make sure the area you select is not interfered with by any hardware or sharp edges in the chimney. The area must have parallel or slightly sloping walls ideally with texture for the balloon to grab and lodge when inflated. Measure the length and depth of the chimney in the location you have selected to install the Pillow. Write down the dimensions. Measure your chimney about 30cm or so up out of sight where your Chimney Pillow will fit as shown in the diagrams. You will need the side-to-side and the front-to-back inside dimensions. We suggest you use a flexible steel tape measure (Stanley type) or two pieces of cardboard extended like wings.
It is only necessary to measure approximately and choose the Chimney Pillow of the approximate size or slightly bigger than your chimney.
How do I choose the correct size Chimney Pillow if there is a smoke shelf or smoke chamber in my chimney?
Sizing Tips On any measured flue opening smaller than 12"X12" you should order a Chimney Pillow the exact size or no more than 3" too large in length or width. On any measured flue opening larger than 12"X12" you should order a Chimney Pillow the exact size or no more than 6" too large in length or width.
It is OK to buy a Chimney Pillow larger than your measured opening as you will be inflating it into place. However, DO NOT by a Chimney Pillow that is too small for the measured opening.