This paper details how to use continuous-flow hypoxia chambers to generate atmospheres with defined concentrations of O2 to understand biological responses to decreased O2. This system is easy to setup and maintain, and flexible enough to suit a wide range of O2 concentrations and model systems
Fawcett, E. M., Horsman, J. W., Miller, D. L. Creating Defined Gaseous Environments to Study the Effects of Hypoxia on C. elegans. J. Vis. Exp. (65), e4088, doi:10.3791/4088 (2012).