Thirdeye posted a great post about this in this thread:
I was wrong, it IS the smoke, not the heat...oh well, just read the post by ThirdEye - he's the expert :)
IMBAS Certified MOINK Ball maker and IMBAS Sgt. At Arms.
And now, brethren, I commend you to God, and to the word of his grace, which is able to build you up, and to give you an inheritance among all them which are sanctified. [Acts 20:32 KJV]