An improved singlet delta oxygen generator (SOG) and method of its use are disclosed. The improved SOG is compact and scalable, capable of operating in a zero-gravity or low gravity environment, requires no gaseous diluent or buffer gas, and is capable of operating at pressures as high as one atmosphere. The improved SOG also efficiently utilizes the reactants and produces a O.sub.2(.sup.1.DELTA.) stream that is largely free of chlorine and water vapor contamination and therefore does not require a BHP regeneration system or a water vapor trap. When used as part of a COIL system, the SOG may be part of a plenum that directly feeds the laser's nozzle. The close proximity of the SOG to the laser cavity allows operation of the SOG at higher pressures without significant depletion of available O.sub.2(.sup.1.DELTA.) through collisional deactivation.