Portable Calibrator for NO Based on Photolysis of N<sub>2</sub>O and a Combined NO<sub>2</sub>/NO/O<sub>3</sub> Source for Field Calibrations of Air Pollution Monitors

Abstract

Abstract. A highly portable calibration source of nitric oxide (NO) based on photolysis of nitrous oxide (N2O) supplied by 8- or 16-g disposable cartridges is demonstrated to serve as an accurate and reliable transfer standard for the calibration of NO monitors in the field. The instrument provides output mixing ratios in the range 0–1,000 ppb with a precision and accuracy of better than the greater of 3 ppb or 3 % of the target NO mixing ratio over a wide range of environmental conditions of ambient temperature (8.5–35.0 °C), pressure (745–1,015 mbar corresponding to 2.7–0.0 km elevation) and relative humidity (0–100 % RH). Combination of the NO calibration source with a previously described ozone calibration source based on photolysis of oxygen in air provides a new instrument capable of outputting calibrated mixing ratios of NO, ozone (O3) and nitrogen dioxide (NO2), where the NO2 is produced by the stoichiometric gas-phase reaction of NO with O3. The portable NO2/NO/O3 calibration source requires no external gas cylinders and can be used for calibrations of NO, NO2 and O3 instruments for mixing ratios up to 1,000, 500, and 1,000 ppb, respectively. This portable calibrator may serve as a convenient transfer standard for field calibrations of ozone and NOx air pollution monitors.