Two IR flash kinetic spectrometers are described. Both use nanosecond pulsed UV lasers to produce high concentrations of reactive species. These are then probed by tunable cw IR lasers. High-resolution spectra of singlet and triplet states of CH2 and of HCO are presented. Measurements of reaction rates and of product quantum yields are described for several reactions important in atmospheric and combustion chemistry with particular emphasis on the dynamics of radical-radical reactions. The reactivity of the coordinatively unsaturated organometallic intermediate cyclopentadienylcobaltmonocarbonyl (CpCoCO) to a variety of ligands is studied in both gas and liquid phases.