Ms Moyagh Murdock:

I am an engineer. I will not say I am a fire expert but I understand the confusion. In an open fire there could be sparks but they are at ground level. The heat generated up a flue is intense and the sparks coming out the top are much closer to the combustible material. That is probably why it is a higher risk. It is not so much the sight of sparks on the ground; it is what comes out at the top-----