Apparatus and methods are disclosed for controlling atmospheric characteristics inside a chamber. An apparatus comprises a mechanism for diffusively introducing pressurized gas into the apparatus, an outlet element in fluid communication with the mechanism, and a chamber in fluid communication with the outlet element. The outlet element and the chamber are disposed such that gas flow therethrough is substantially uniform. The chamber comprises a gas outlet and the outlet element comprises a plurality of openings. The apparatus may be employed in the manufacture of biopolymers on the surface of a support such as an array of biopolymer features on the support.
