The properties of PM steel are affected by the oxygen content of the material. The surface oxides on the powder grains are an important source of oxygen in steel produced from powder, and it is therefore interesting to investigate under what conditions the surface oxides are formed, and can be reduced. In the present work Photo Acoustic Spectroscopy (PAS) studies were used to study surface oxides on powders. The measurements were coupled with thermodynamic calculations, to identify the type of oxides. The use of the PAS instrument is a novel technique for gas analysis at ppm levels under controlled atmospheres and heat treatments. Examples are shown from studies of oxide reduction, furnace atmosphere control, and moisture uptake. Sintered steel, stainless steel, and low alloyed steels were investigated. The accuracy and reproducibility of the method for different applications is assessed.