Customer had smoke alarm, set off and called service to check out furnace. On inspection scope found separation in heat exchanger pictures attached to file. System had been off when arrived. CO detector testing at zero in the house started furnace and tested video showing flame rolled out and after consistent running CO detector was reading 2PPM after about 10 to 15 minutes. Some windows were open in the house, providing some ventilation to reduce overall CO levels. System should not be run and upgrade necessary as repair is not a viable option.