Rogier Evertsen of the University of Nijmegen in the Netherlands has demonstrated the suitability of cavity ringdown spectroscopy for the analysis of the combustion products of fuel flames. In a report of the work that appeared as his doctoral thesis, Evertsen demonstrated that the approach can detect OH, CH, HCO, NO and NO2 from burning methane, oxyacetylene and diesel fuel.Pulsed cavity ringdown spectroscopy proved sensitive to NO and NO2 at concentrations of 25 ppm and 3 ppm, respectively, which is within the requirements established in Europe for the detection of NOx compounds. Evertsen said that combining the technique with other approaches, such as laser-induced fluorescence spectroscopy, may enable the fast and quantitative study of combustion processes.