Molten sodium (623 to 69°K) was injected by a pneumatic, piston spray-injector into a closed reaction chamber containing dry air or dry air-nitrogen mixtures. The rate of the pressure rise resulting from the sodium-air burning reaction was measured during the spraying interval. The pressure-rise rate was a measure of the reaction rate. The spray particle size had the most pronounced effect on the reaction rate, which increased as the particle size decreased. Increasing the spray velocity resulted in a modest increase in the reaction rate. The reaction rate decreased slowly as the oxygen content of the atmosphere was lowered until, at an oxygen concentration of 4 mol%, there was no visible burning.