Performed preventative maintenance for 4 zone high efficiency boiler with 1 zone indirect domestic tank per maintenance agreement. Cleaned out the burner compartment and the buildup within the drain. Tested all 4 zones for proper operating. Inspected all electrical components. Inspected all water pipes for no leaks. Boiler is operating at 15psi with a temperature of 175°F. Performed a combustion analysis on boiler. System is operating at 95% efficiency with a CO level of 7ppm. System is operating properly at this time. System is operating properly at this time.