In October of 1976, the U.S. Environmental Protection Agency announced that the calibration procedure then currently in use for reference methods for the measurement of ozone in the atmosphere -- the neutral buffered potassium iodide procedure -- had been found variable and in some cases inaccurate and would be discarded. Four alternative calibration methods would be investigated as possible replacements: the ultraviolet photometry procedure, the gas phase titration with excess nitric oxide procedure, the gas phase titration with excess nitric oxide procedure, the gas phase titration with excess ozone procedure, and the boric acid-potassium iodide procedure. This publication summarizes the evaluation effort of the U.S. Environmental Protection Agency to select an alternative calibration procedure. Each method was subjected to a preliminary investigation to review the procedural descriptions and to assess the critical performance parameters. Variability studies were subsequently conducted to estimate the precision and accuracy of ozone calibrations using the four methods. The results of these studies were then compared. The ultraviolet photometry procedure was determined to be the most dependable and accurate and was designated the replacement procedure.

"November 1980." "EPA-600/4-80-050." "PB81-118911.' Microfiche.