More precise and accurate parts-per-billion level calibration gases are obtained dynamically from concentrated sources such as permeation tubes and pure pressurized gases. Calibration gas production is accomplished by multistage dilution steps, comprised of combinations of pneumatic and diffusion processes. Zero air is defined relative to an analyzer response including interferent molecular response. Dilution precision and stability can be obtained within ±1 percent over ±15°C variations with pneumatic/pneumatic and pneumatic/diffusion networks. Nitric oxide calibration gas is generated from a nitrogen dioxide permeation tube and a molybdenum converter. Dilution factors larger than one billion are obtained with multistage pneumatic/diffusion techniques. The parametric relationships at each dilution stage are defined and the theoretical performance limits of multistage dilution techniques established.