I couldn't believe it! I had never heard of "chimney balloons" until I was made aware of them by a comment on the post about the "standby power controller" (see http://no-cobwebs-gxh.blogspot.com.au/2012/10/the-spc.html ). Next day, the doorbell rings - and there's a person offering us our "free chimney balloons"!
The thought crossed my mind that perhaps the chimney balloon people are linked to the SPC people. Or was the timing really a coincidence?
Be that as it may, I am greatly indebted to the comment on the SPC posting alerting me to the existence of this product, otherwise I would have had no idea at all what it was. As it happened, I was able to decline the product with grace, saying that I was aware of the product, but we preferred not to have it (mainly because we actually use the main fireplace in our house). Hence the image here has been obtained from the internet.