An organic printing deposition system, comprising: a print head comprising: a nozzle block comprising a delivery aperture, the delivery aperture being in fluid communication with a source of organic material to be deposited on a substrate by the printing deposition system; one or more shield gas distribution channels (501, 502), each shield gas distribution channel being disposed above or below the delivery aperture when viewed from below the nozzle block; and one or more exhaust channels disposed adjacent to the delivery aperture such that, during operation of the print head, non-condensing gas flow generated by the delivery aperture is captured by an exhaust aperture; wherein each of the one or more shield gas distribution channels is arranged to provide a flow of shield gas that prevents material from a chamber ambient in which the print head is operated from reaching the exhaust apertures of the nozzle block, wherein the shield gas apertures are provided by nozzles surrounding the print head containing the nozzle block, characterised in that the system further comprises a plurality of shield gas apertures, each of which ejects shield gas into the space between the substrate and the print head during operation of the print head such that all gas ingested by the exhaust apertures originates from either the delivery aperture or one or more of the shield gas apertures, wherein the shield gas apertures are located on a chiller plate (1501, 1801, 2101, 2204) between the print head and substrate, whereby the chiller plate is cooled. a print head comprising: a nozzle block comprising a delivery aperture, the delivery aperture being in fluid communication with a source of organic material to be deposited on a substrate by the printing deposition system; one or more shield gas distribution channels (501, 502), each shield gas distribution channel being disposed above or below the delivery aperture when viewed from below the nozzle block; and one or more exhaust channels disposed adjacent to the delivery aperture such that, during operation of the print head, non-condensing gas flow generated by the delivery aperture is captured by an exhaust aperture; a nozzle block comprising a delivery aperture, the delivery aperture being in fluid communication with a source of organic material to be deposited on a substrate by the printing deposition system; one or more shield gas distribution channels (501, 502), each shield gas distribution channel being disposed above or below the delivery aperture when viewed from below the nozzle block; and one or more exhaust channels disposed adjacent to the delivery aperture such that, during operation of the print head, non-condensing gas flow generated by the delivery aperture is captured by an exhaust aperture; wherein each of the one or more shield gas distribution channels is arranged to provide a flow of shield gas that prevents material from a chamber ambient in which the print head is operated from reaching the exhaust apertures of the nozzle block, wherein the shield gas apertures are provided by nozzles surrounding the print head containing the nozzle block, characterised in that the system further comprises a plurality of shield gas apertures, each of which ejects shield gas into the space between the substrate and the print head during operation of the print head such that all gas ingested by the exhaust apertures originates from either the delivery aperture or one or more of the shield gas apertures, wherein the shield gas apertures are located on a chiller plate (1501, 1801, 2101, 2204) between the print head and substrate, whereby the chiller plate is cooled.