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SIMULTANEOUS CALIBRATION OF OPEN-PATH AND CONVENTIONAL POINT MONITORS FOR MEASURING AMBIENT AIR CONCENTRATIONS OF SULPHUR DIOXIDE, OZONE, AND NITROGEN DIOXIDE
Citation:
McElroy, F., J. Hodgeson, T. Lumpkin, K. Rehme, R. Stevens, C. Conner, AND H. Hallstadius. SIMULTANEOUS CALIBRATION OF OPEN-PATH AND CONVENTIONAL POINT MONITORS FOR MEASURING AMBIENT AIR CONCENTRATIONS OF SULPHUR DIOXIDE, OZONE, AND NITROGEN DIOXIDE. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/A-93/251.
Description:
A two-stage dilution system and an associated procedure to simultaneously calibrate both open-path (long-path) and conventional point air monitors have been used successfully during a comparison test study of open-path monitoring systems in Houston during August, 1 993. wo open-path, differential optical absorption spectrometers (DOAS) were calibrated using standard concentrations up to 50 ppm in a 0.9 meter stainless steel optical cell connected to each DOAS analyzer via fiber optic cables. he calibration apparatus consisted of various flow controllers, flow meters, and mixing chambers to provide accurate dynamic flow dilutions; a high-concentration ozone generator; a suitable reaction chamber for gas phase titration (GPT) of NO to generate NO2 Standard concentrations; and an output manifold. igh concentration standards for S02 and NO were obtained by the primary dilution of nominal 1000-ppm, NIST-traceable concentration standards in compressed gas cylinders. O2 concentrations were generated by GPT from NO concentrations. he ambient-level concentration standards were provided by quantitative secondary dilution of the high concentration standards. zone standard concentrations were generated by the high-concentration ozone generator and assayed, after secondary dilution to ambient level concentrations, by a commercially available UV photometric ozone analyzer used as a transfer standard.