The present invention relates to a method for producing and delivering a gas mixture having a selected composition of a first gas and at least one second gas, comprising the following steps: (a) providing a main gas flow comprising the first gas in a main conduit, (b) separating the main gas flow into a first plurality of secondary gas flows, (c) guiding each secondary gas flow through a secondary conduit, (d) adding at least one second gas to at least one of the first plurality of secondary gas flows in the respective secondary conduit through a delivering conduit, said delivering conduit protruding into the secondary conduit, and (e) combining the first plurality of secondary gas flows to the gas mixture. With the technical teaching of the present invention a dynamic gas bottle filling is possible wherein the second gas components may have a concentration form some ppb to percent.