Feedback Flow and Permeation Systems for the Calibration of Very Low Gas Concentrations Available to Purchase

The authors have developed two new absolute calibration techniques for low levels of atmospheric gases, using pure starting materials. The feedback flow system is a multistage dilution device with unreactive components, in which pure material is repetitively diluted with a single flow of zero gas, making available small flows of gas over the whole range from parts per trillion to percentages in one run. The permeation system is an extension of the work of Dietz et al, in which a sensitive low-cost system allows typical permeation rates to be measured in a few minutes.