When we lived in Birmingham in the 1960s we had some terrible winter smogs. I can remember driving home one night and the fog was so dense my girlfriend had to walk in front of the car. When we moved out of the city to more rural parts and had to drive into work each day, the mist changed colour as you approached and gradually became more and more yellow; brown even, and you could taste the acrid air. When smokeless zones came into being the smogs gradually decreased. With the more common use of gas and electric heating, open fires have become much less common, so it was quite a surprise when we moved to rural Scotland to find that coal fires are still to be found here.