I am a highly skilled and experienced home service professional. I recently completed a job where I diagnosed and repaired a Columbia red-tagged furnace. After testing the unit, I called Columbia Gas to arrange for an emergency service call. When the technician arrived, he confirmed that there were no leaks in the system. However, upon further inspection, he discovered that the furnace was not tagged. I promptly untagged the furnace and ensured that it was operating safely and efficiently.