Square Large Chimney Balloon - 31cm x 31cm (12" x 12")


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For chimney sizes up to 31cm x 31cm (12" x 12"). Large square chimney balloons are ideal for lined flues (i.e. the terracotta block liners which are used to build modern chimney stacks).

A chimney balloon is a simple and efficient way to stop the loss of warm air from your room up the chimney, and the flow of cold air from outside coming down the chimney. It stops draughts, heat loss, soot, debris, and birds' mess, as well as reducing noise.

How does it work?

The Chimney Balloon is like a plastic pillow. You put it about a foot up the chimney, holding it by the handgrip to keep your hands clean. You then inflate the balloon until it grips the chimney walls. When it is fully inflated you turn off its tap. Your chimney will no longer draw warm air out of your room.

Air movement before balloon air movement after balloon

The chimney balloon is not rubber, because rubber perishes in chimneys. It is actually made from a fairly thin but flexible plastic tri-laminate, a special 'hi-tech' material. The outer layer is tough, the inner is an air barrier layer and the core is a heat-shrink material. It is transparent to aid fitting.

Why use one?

Chimneys are great at drawing warm air out of the room, and that is just what you need when the fire is lit and there is smoke in the air. The problem is that chimneys continue to work even when the fire is not lit. If you put your hand down to the floor boards or around a window can you feel a cold draught coming in? Where do you think all that air goes?

You could improvise and block your chimney with planks of wood, blankets, bricks, newspaper, or a combination of these. The problem with this approach is that it is ugly, difficult to remove if you want to light the fire, and won't let the chimney breathe (to stop damp developing). You could also seal the chimney from the top, but that would cost a lot of money and put an end to you lighting the fire when you want. Or maybe you could pinch a party balloon from a child and put that in the chimney. If it doesn't burst straight away, it will probably deflate over the next few days.

The answer is to use a balloon that has been specifically designed to block the chimney. Our chimney balloons will stay inflated and in place for years. They provide the right seal (with small air gaps for ventilation) for the chimney and can be reused by deflating and re-inflating as many times as you want.

Measuring your chimney

You measure the chimney about a foot or two above the top of the fireplace opening. Make sure that the place where you plan to put the balloon has walls that are parallel to each other and ensure that the seven to eight inches of handgrip are out of sight up the chimney.

balloon position 1 balloon position 2 balloon position 3

You will need to measure both the side to side and back to front inside dimensions at the position you will place your balloon. The best way is to use a flexible steel tape measure or a piece of string (which you size to length inside the chimney and then measure). Choose a chimney balloon that is the same size or bigger as your chimney in both dimensions. If you choose a balloon that is smaller in either direction, it will not stop the flow of air in your chimney. Tip: you could try counting the number of bricks on the inside of your chimney and multiplying that by the measurement of one brick to estimate the size balloon you need.

where to measure

Alternatively, see our chimney sizing table here.

The chimney balloon comes in five standard sizes:

  • Small: For chimney sizes up to 38cm x 23cm (15" x 9").
  • Medium: For chimney sizes up to 60cm x 30cm (24" x 12").
  • Large: For chimney sizes up to 90cm x 38cm (36" x 15").
  • Square small: For chimney sizes up to 23cm x 23cm (9" x 9").
  • Square large: For chimney sizes up to 31cm x 31cm (12" x 12").

For further instructions, follow this link.

  • Manufactured by: Chimney Balloon