On March 25th 2019 at 19:49 hrs, Station 18 Folsom Fire Company was dispatched to 529 Folsom Ave for a CO Alarm. Upon the arrival of ENG 18 found the occupants outside the structure, the crew entered the structure with the gas meter and found a reading of 3PPM on the upper floors. PECO was requested. The occupants stated they had been using an unvented propane gas fireplace in the building. The company was in service for20 minutes under the command of Chief Joe Carollo.