Firewood that hasn't been used and is rotting outdoors should never be burned inside. Some of that wood may have fungus and bacteria that could be distributed inside your home when you burn it. Instead, leave the rotting wood outdoors to become a habitat for animals and insects. Just keep the rotting wood away from healthy trees, since the fungus, bacteria and disease could transfer to them. And try to find a shady spot -- that environment mimics where wood piles would be found in nature.
ANDREWS MCMEEL SYNDICATION