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Measurement of nitrogen dioxide (N0 2 ) and other oxidized nitrogen compounds in indoor environments can present some measurement difficulties not normally encountered in sampling outdoor air. This paper examines three methods that are in current use for monitoring indoor nitrogen dioxide. The methods include ozone-based and luminol-based chemiluminescence, and an electrochemical technique. We have examined these methods for accuracy, linear dynamic range, and interferences. Each of the methods was subject to interference. For indoor measurements, nitrous acid probably represents the most significant interference for the ozone-based chemiluminescence and electrochemical monitors.

The gas phase reaction of NzOs with water vapor was investigated in a 17.3-m' Teflon lined chamber. Temporal concentration profiles for ozone, total nitrogen oxides, and nitrogen dioxide were measured. Concentration profiles for N2OS and HNO, were calculated from a combination of measurements of nitrogenous species. A kinetic mechanism with an adjustable value for the rate constant of NzOs + H,O was used to model the experiments. From this analysis an upper limit value of k s 4 x 1 0~ ' ppm min-' for the gas phase reaction N,O, + HzO + 2HNOi was derived.