The Model 410 Nitric Oxide Monitor? is designed for the measurement of atmospheric nitric oxide (NO) in the concentrtion range 0-2,000 ppb (0-2 ppm) with a precison of ±1.5 ppb. When used in combination with the Model 401 NO₂ Converter, NO_x and NO₂ (by difference) are also measured. The detection principle of the Model 410 is based on the selective reaction of NO with ozone. The resulting ozone depletion is measured using the absolute method of UV absorbance and thus requires only infrequent calibration. By comparison, chemiluminescence NO_x instruments require nearly continuous calibration using a standard gas.