How to measure for a chimney balloon

What Size Chimney Balloon You Require

Chimney Balloons come in six standard sizes. The vast majority of houses built during the 1970s or later will tend to have a lined round shaped flue. It is always best to double check before purchasing though. Follow the below steps

1:Use a torch to view up the inside of your chimney. Establish whether you have a round, square or rectangular or round shaped flue.

2: If its is round order the 7-9 Round Balloon

3: If it is a square or rectangular chimney you will need to locate two straight or parallel walls to where the chimney balloon will rest once inflated. (See Diagrams)

If it is square the options are 9×9 Inch or 12×12 Inch. If it is rectangular your options are 15×9, 24×12 or 36×15 Inch.

4: Measure this area front to back and side to side and compare measurements with the standard sizes available to establish which size you require.

5: If the sizes are not exact always go for balloon size which is slightly above your measurements.

Order a Chimney Balloon Now.

Find out how to fit the chimney balloon

Find out why you need an inflation tube to install a chimney balloon

Find out about Other Chimney Balloon Accessories to make installation easier


  1. I’ve purchased a chimney balloon from you before, and I’ve measured an upstairs bedroom and the your website isn’t displaying the measuremant or size that I need. I’ve measure wide 17 x 12 and that is from left to righ of the opening = 17 incheches and from the back to the front of the flue is 12 inches.. so I’m assuming the 15 x 12 inch rectangular product will do. As I said I can’t see the images on the website to find the correct balloon. Can you reply at your ealiest convenience.


    1. Hi Frank,

      Perhaps you are measuring at the incorrect place. You should be measuring about 1 foot up from the the fireplace (where the chimney begins to narrow)

      If the house was built since the 1970s it is most likely a round shaped flue and thus you would need the 7-9 Inch Round Balloon.

      However it is not uncommon for the measurements not to meet the exact dimensions of the sizes readily available. The rule of thumb in this instance is always size up.

      If the dimensions are 17×12 I suggest going with the 24×12 size balloon.

      Let me know if you got any further questions.



    1. Hi Ross,
      Best to get a torch out and see if the space narrows further up the chimney. It generally would within 2 feet of the fireplace. If it does measure side to side and front to back of the narrow area and one of the standard sizes should fit well. If it doesn’t give us a call in Dublin on 01 8428187 (Call 00 353 1 8428187 if you are calling from outside Ireland) and we can arrange to have a customised size balloon made for you.

  2. I have a 15 x 15 inch square chimney . Should I be ordering a 36 inch x 15 inch or is that too big? The other dimensions available are too small

    1. Hi David,
      Are you sure you are measuring in the correct place? You should measure up the chimney where the flue begins to narrow. This is usually between 1 to 2 feet up the chimney. If you are measuring in the correct place we can arrange to have a customised size ordered in for you. It will cost a little bit extra and it might take a week or so to get to you but it can be done.
      Of course you could try the 36 x 15 installed at an angle but it would not be ideal. If the house is built for the 19 70s onwards the chances are that you require the 7-9 Inch round balloon though.
      Feel free to call us after the weekend and we can go through it in more detail. Contact us on 01 8428187

  3. Hello, I have no idea how to Krause my chimney. I simply cannot get up there past the fireplace. There is a gap where I have removed a grate which is about a foot wide but I cannot get far enough into the chimney to measure the walls. Please could you advice? Perhaps I am missing something.

    1. Hi Sean if your house was built in the 1970s or later and the gay you refer to is round I would imagine you require a 7-9 inch balloon. If it is difficult to reach you might also consider getting an extended handgrip and a spare tap to make it easier to install.

  4. Hello. I have a chimney in a house built in the 1930s. I have read the comments in your answers above and see that about 2 -3 feet above the top of the wide area above my fireplace and above the smoke chamber that the flue is round but cannot get far enough up to measure it as the shelf above the fire sits quite far forward. The chimney cleaner from memory says it’s likely a 6-9 inch. Am I best to get the 7-9 inch round one so?

    Thanks very much.

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