Hi there - I have a client in San Diego, CA who would like to close off their existing gas fireplace. They don't want to remove the chimney or anything on the exterior, they just want to drywall over the fireplace and cap the gas line to make it go away. Would this be allowed and/or would they have to remove the exterior chimney? I've never encountered anyone who wanted to eliminate a working fireplace before so was not sure! Thanks so much!