Collection of In-Stack NO2/NOx Ratio Information

Collection of In-Stack NO2/NOx Ratio Information

Dan Dix was recently an invited guest at U.S. EPA’s 10^th Conference of Air Quality Modeling where he presented on the “Collection of In-Stack NOX/NO2 Ratio Information.”  With the promulgation of the new 1-hour nitrogen dioxide (NO2) National Ambient Air Quality Standard (NAAQS) the use of AERMOD’s Tier III option, which incorporates chemical transformation of oxides of nitrogen (NOX) to NO2, has been relied on more to show compliance with the new standard.  Currently U.S. EPA allows the use of a default in-stack NOX/NO2 ratio of 50% (a key variable for using the Tier III option) in the absence of appropriate data.  Dan’s presentation outlined an easy and cost effective way to collect in-stack NOX/NO2 ratio data from facilities that currently have NOX Continuous Emission Monitoring Systems (CEMS) in place.