With a closed-loop dynamic gas control system, the Oxystreamer maintains mixed gas concentration to within 0.2% of the selected set-point levels. Ranges cover O
2 concentration from 0.1 to 99.9%; CO
2 concentration from 0.1 to 20.0%; N
2 concentration 0 to 100%. The two output streams of this system are useful for controlling the atmosphere in a microscope stage mount cell culture incubator/chamber and the dissolved O2
2 and CO
2 levels in a media or perfusate. This system provides precise and variable selection of O
2 and CO
2 gas concentrations.