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All about hot air

Chimneys act like a funnel to take warm air away. This is a good thing when your warm air is full of smoke! But chimneys work hard even when there is no fire. Here's why...

Warm air rises, cold air sinks

We all know how hot-air balloons work, right? But have you also wondered why cold air rushes in through the gaps in the floors, doors and windows? (maybe even down the chimney!?) This occurs due to nature's most simple law of physics: hot air rises, cold air sinks. That is to say: air which is relatively warmer than its surroundings will rise; cooler air, by contrast, sinks. This process continues until either the air is trapped at the ceiling (or at the floor), or the temperatures equalise.

The trick with volume

Interestingly, cool air flowing down into your room can't get in unless there's warm air flowing out at the same speed. In other words, the volume of air must remain constant. If not, we'll experience a change in atmospheric pressure.

So what happens when a large volume of warm air moving up is trapped by an equal or larger volume of cold air moving down? The two contrasting volumes of air will rush past each other violently, often causing 'funnels', or tornadoes.

So how do we prevent our cosy warm air from escaping up our chimney?

The options

You could block your fireplace with a board or bricks but – then it looks ugly, and you can't use your fire when you feel like it. Also, you'll find your chimney will get damp because the bricks aren't breathing...

You could stuff newspapers up the chimney throat, but they won't be efficient, will probably shift over time, and (of course) are a potential fire risk.

You could stick a seal on the top of the chimney, but this could be expensive, and you can forget lighting fires! Even worse, you will still be heating a large volume of air in the chimney.

OK – so get an ordinary balloon, inflate it and stick it in the chimney... BANG! (whoops, sorry) even if it doesn't burst at once, it will shrivel up within a day! That's why you need our specially-engineered, guaranteed, patented Chimney Balloon.

Chimney Balloon is the answer

  • It will stay in place for years – and stay inflated.
  • It will provide 'double glazing' for your fireplace.
  • You can deflate it (and re-inflate it) any time you want a fire.
  • Even if you forget it (and light a fire) it will just shrink and melt harmlessly.
  • Best of all, it's cheap and readily available.

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