An apparatus for producing a three-dimensional work piece, the apparatus comprises a process chamber accommodating a carrier for receiving a raw material powder, an irradiation device for selectively irradiating electromagnetic or particle radiation onto the raw material powder on the carrier in order to produce a work piece made of said raw material powder by an additive layer construction method, a first gas inlet for supplying gas to the process chamber and a gas outlet for discharging gas from the process chamber, wherein the first gas inlet and the gas outlet are configured and arranged in such a manner that a first gas flow across the carrier is generated, a transmission element which allows the transmission of the electromagnetic or particle radiation emitted by the irradiation device into the process chamber, and a second gas inlet for supplying gas to the process chamber, wherein the second gas inlet is configured and arranged in such a manner that a second gas flow in a direction facing away from the transmission element is generated.