Abstract: A method of reducing the proportion of oxygen in an at least partly formed package before product is filled into the package in a filling station in a filling machine, where the package comprises a tube-shaped blank of packaging material, the blank being closed in a first end and open in a second end. The method involves, during transport of the package to the filling station from an immediately preceding station in the filling machine, passing the package beneath a supply means for inert gas, and when the package passes the supply means generating a gas pulse in a direction down into the package. An apparatus is provided for reducing the method into practice.