Combustion Analyzer Calibration

I have a UEI Combustion Gas Analyzer that needs calibration and replacement of the 02 sensor. I checked the UEI website and they advertise calibration service and sensor replacement is available.

Has anyone out there sent a UEI Combustion Gas Analyzer in for calibration and service? Is there anywhere else that services UEI equipment or does it have to go back to the factory for service? I went through this with a Bacharach meter a while back and NACHI had a deal on calibration services.