Lichens on indoor stone fireplace
I just purchased a home that has lichens all over the stones on the indoor fireplace. This fireplace is about 14 feet high floor to ceiling (so large one to clean). The prior owners didn't ever clean the stones on the fireplace in over a decade, so these lichens have been growing for some time. I am curious what is the best way to clean this off (including should I first scrape all of the lichen off with a nylon bristle brush while wearing a mask of course and then using a liquid mixture to wipe down each stone) as one of my sons has a respiratory illness and I don't want anything to stay in the air to harm him. I am also wondering what is best to not only clean them off but prevent them from coming back. Finally, do you think the lichens are on the inside of the chimney (so would I need to clean that too) especially if the fireplace was used a great deal? Thank you for your help!
Scotts Bluff County Nebraska