Preventative maintenence inspection on two Carrier high efficiency furnaces running in great condition. Both air filters are in decent condition. Check again in 1-2 months. Clean flame sensors and checked ignitors. Visual inspection of burners. Flush condensation traps and drain lines. Basement system humidifier pad in new condition. Test ran systems in heating mode from thermostats. Both systems are operating properly and within specs for temperature rise, blower and inducer motor amp draw, and manifold gas pressures. Pvc flue vents in good condition and no sign of leaks. 0PPM CO detected during testing. Systems are operating properly, efficiently and ready for Winter. Performed air balance on second and third floor to get more air into kids bedrooms. Noise heard in basement is most likely duct work expanding and contracting. Will pass along information to construction department.