I have a limestone fireplace and mantle. It has several coats of paint. Any suggestions for stripping it safely, as in no methyl chloride or similar. Know of any mechanical strippers that would work as in pin strippers?

Try some liquid cooking oil. Rub a coat on and let it sit. It should soften and swell the paint. On another site, I was asked how to remove paint from rocks without harming the moss on them. I wasn't sure, but suggested the cooking oil. It worked, the person was very happy, perhaps more complimentary over it that any of the other thousands of answers I have given on the net.

I don't know that anything short of sand blasting will remove the last traces of paint from masonry. The oil will soak into the pores of the rock. It will take repeated washing with soap and water over a period to remove it. I cringe every time I hear of somebody going to paint brick or stone.