In September 2001 Procal’s Philippines distributor, Uniwell Technologies Inc, installed and commissioned a Procal emission monitoring system at the Toledo coal-fired powerplant on Cebu Island. The Procal system comprises two P200 in-situ analyzer probes mounted in each of the boiler outlet ducts to the common chimney. The analysers measure SO2, NO, NO2 and the readings are displayed on a PC running Procal ACWn Windows software. Early in the life of the CEM system there were premature failures of the probe head cooling fans. This was traced to flue gas leaking from nearby vents which were inadvertently left open, allowing flue gas to be ingested by the cooling fans. The vents were plugged, the cooling fans were replaced and the system has run well since. Toledo powerplant staff queried the low NO2 readings from the Procal analyzer probes. They had done some comparison tests with third party extractive instruments which suggested much higher levels of NO2. Twin Tek attended site and carried out water vapour checks to make sure no cross sensitivity was occurring. These proved to be inconsequential. Afterwards Toledo accepted that normally NO2 emitted from coal fired powerplants is rather low.