Came out today to perform preventative maintenance on a Lennox furnace model #SL280UH090V36B-04, serial #5915L04357 and a Aprilaire humidifier 700 series. Upon arrival the homeowner stated that they had some roof damage and upon repair they found that the chimney was damaged as well. The homeowner is waiting on the insurance for the repair but wants to verify that her furnace is safe to operate. I powered the system on and called for heat. I took a combustion analysis test and received the following readings, o2 is 9.9% and the co levels 6ppm . The supply temp is 118°F. The inducer motor amp draw is .22 and the blower motor amp draw is 5.7. I powered the system down and removed the access panels. I removed and cleaned carbon off of the flame sensor and cleaned out the burners and burner box. Checked all electrical connections to ensure that they are secure and in good condition. Installed a 16x25x1 air filter until the homeowner can get a new Merv filter. Checked the pressure switch fo