An apparatus for producing a three-dimensional workpiece via an additive layer construction method, the apparatus comprising: a carrier adapted to receive material for producing the three-dimensional workpiece; a material supply unit adapted to supply material to the carrier and/or preceding material layers on top of the carrier, a layer depositing mechanism for forming the supplied material into a material layer on top of the carrier and/or the preceding material layers on top of the carrier, a solidification device adapted to solidify the material supplied to the carrier and/or the preceding material layers on top of the carrier for producing the three-dimensional workpiece, a gas supply unit adapted to supply a shielding gas to an area of the material layer that is to be solidified by the solidification device, a process chamber comprising the gas supply unit and the solidification device, a moving unit adapted to move the process chamber relative to the carrier, and a positioning system adapted to determine a position of the process chamber relative to the carrier, wherein the process chamber further comprises one or more of: a gas flow device adapted to form a flow of gas above a surface of the area of the material layer that is to be solidified by the solidification device, a heating unit adapted to heat up the material supplied on the carrier, and a safety device or part of a safety device adapted to prevent, during operation of the apparatus, release of process emissions to a surrounding of the process chamber, wherein at least one of the gas flow device, the heating unit and the safety device or part of the safety device of the process chamber is adapted to operate independently of a moving direction of the process chamber; wherein the process chamber comprises a multi-wall structure, and wherein a first cavity formed between a first wall and a second wall of the multi-wall structure is comprised in or coupled to the material supply unit. a carrier adapted to receive material for producing the three-dimensional workpiece; a material supply unit adapted to supply material to the carrier and/or preceding material layers on top of the carrier, a layer depositing mechanism for forming the supplied material into a material layer on top of the carrier and/or the preceding material layers on top of the carrier, a solidification device adapted to solidify the material supplied to the carrier and/or the preceding material layers on top of the carrier for producing the three-dimensional workpiece, a gas supply unit adapted to supply a shielding gas to an area of the material layer that is to be solidified by the solidification device, a process chamber comprising the gas supply unit and the solidification device, a moving unit adapted to move the process chamber relative to the carrier, and a positioning system adapted to determine a position of the process chamber relative to the carrier, wherein the process chamber further comprises one or more of: a gas flow device adapted to form a flow of gas above a surface of the area of the material layer that is to be solidified by the solidification device, a heating unit adapted to heat up the material supplied on the carrier, and a gas flow device adapted to form a flow of gas above a surface of the area of the material layer that is to be solidified by the solidification device, a heating unit adapted to heat up the material supplied on the carrier, and a safety device or part of a safety device adapted to prevent, during operation of the apparatus, release of process emissions to a surrounding of the process chamber, wherein at least one of the gas flow device, the heating unit and the safety device or part of the safety device of the process chamber is adapted to operate independently of a moving direction of the process chamber; wherein the process chamber comprises a multi-wall structure, and wherein a first cavity formed between a first wall and a second wall of the multi-wall structure is comprised in or coupled to the material supply unit.