This report is related to nitrogen oxide (NOx) emission, concentration and reduction at the area of Ishigaki Domestic Airport. Field investigation to grasp NOx concentration around the Ishigaki Airport andexamination of an effectiveness of photo catalysis on NOx reduction were carried out.
　From the investigation, following conclusions are obtained.
　1) It is found that the NOx concentration along the main runway is related to aircraft moving direction.
　2) Airport is one of the largest emission sources of NOx.
　3) It is confirmed that the NOx concentration can be reduced about 10 percent by an application of TiO2-photo catalysis.
　4) High-concentration of NOx are also detected at the parking area in the airport, due to cars passing nearthe measurement points at a low speed.