Standard atmosphere generator: a dynamic system for the controlled dilution of organic vapours in air
An apparatus is described for the production of standard atmospheres of compounds at the concentrations normally encountered in air pollution studies. It is a glass-blown, flow system with continuous syringe injection of the compounds into a vaporiser, prior to their dilution in the main flow line. Statistical analyses of performance tests on a range of compounds show that stable atmospheres are produced within 5 min of start-up. The instrument produces the predicted concentrations of non-polar compounds with a high degree of accuracy, and tests on atmospheres of a relatively involatile compound, l-methylnaphthalene, reveal no diminution in performance even with concentrations approaching that of its saturated vapour.