[Glenn]

That same type thing is caused by grinding sparks so you may want to aim the grinder another direction if that is the reason.

If you have an open forge, try a chimney. If you use a chimney already try adding another section to the chimney to make it taller, and a wire screen at the top.

An air blast that does not blow the coke out of the fire pot will go a long way in reducing hot sparks up the chimney. This may mean building a deeper or even larger fire than you have now.

Photos of your set up will go a long way in explaining the problem. After we see what we are dealing with, we can be more specific with our suggestions.