At approximately 15:40 Bryn Mawr Fire Company was dispatched to 9 Cricket Terrace in the Lower Merion section of Ardmore with an engine to assist Station 25 on a CO call. Merion Fire Company had been dispatched for a fire alarm and quickly learned that they had a serious CO problem originating from an electrical issue with the underground equipment out front. With readings nearing 2000 ppm crews carefully checked the surrounding structures and provided ventilation as PECO worked to resolve the electrical equipment issue.