L-PBF (Laser Powder Bed Fusion) is a layer by layer 3D manufacturing technique similar to the laser welding process where it is common knowledge that the interaction between material laser and gas is of great importance. Used metals like aluminum or titanium tend to form oxides or nitrides in the presence of the corresponding gas influencing the chemical and mechanical properties. In L-PBF establishing process conditions means purging the process chamber with an inert gas (nitrogen or argon) to an oxygen concentration of around 1000 ppm replacing the air inside. To understand the effect of residual oxygen on aluminum based alloy AlSi10Mg parts this paper will show a parameter study at 100 ppm oxygen in the process chamber compared with 1000 ppm. Finally it will be investigated how oxygen affects final parts regarding porosity and microstructure. By reducing the oxygen concentration lower porosity could be reached at higher scanning speed.