I have decided that my current setup is not safe to burn. I have a Fisher insert in a fireplace without any connections to ceramic/brick chimney. Last year we had at least 2 small chimney fires with a lot of creosote build up. I am planning to put in a Regency insert with a full flex liner. The question I have is that the chimney has a build up of the shiney creosote. If this creosote is not removed prior to the new liner could it get to a high enough temperature to spontaniously combust in the airspace of the chimney. Thank you for any help.