Perform the maintenance for one oil fired hot water boiler, replaced the oil nozzle, oil filter and pump screen. Opened the top of the boiler and brushed out the heat exchanger and vacuumed. Started up the boiler and confirmed operation, confirm that the AquaStat is working correctly and turning the boiler on and off at the correct temperature. Performed a combustion test on the boiler, noted that the CO reading is higher than it should be however there is a lot of dust buildup inside from the dryer which is causing air to slow down because of buildup on the blower wheel. I recommend that next year we remove the motor and pump assembly and clean the blower wheel out and remove all the lint from inside. The boiler is running and operating properly at this time.