Optimization of O3 Monitor NAAQS Compliance Networks - II OTC/MANE-VU Committee Meeting Hall of States 444 N. Capitol Street, NW Washington, D.C. September 20, 2016 Will Ollison (American Petroleum Institute) 1220 L Street, NW • Washington, DC 20005-4070 • www.api.org

Unfinished Business Recommendation – O3 design value (DV) monitor “interference-free” upgrades benefit compliance by reducing photometer positive interference bias; however, TAPI T265 NO-CL FRM upgrades should adjust for ambient humidity since Nafion-dried ambient samples concentrate ambient O3 by up to 4% (3 ppb @ 70 ppb) 2B 211 NO-scrubbed FEM upgrades should consider equalizing N2O-conserving unequal dilutions of sample & reference photometer flows which permit 1-3% of local interferences present to remain. 1220 L Street, NW • Washington, DC 20005-4070 • www.api.org

Unfinished Business Recommendation - Lowering DV site inlets to 2 meters above ground level benefit compliance under stagnant conditions due to enhanced O3 surface deposition and better match ambient outdoor nose heights; however, Allowable 2-15 m inlets must be 1 m distant from shelter surfaces, but sites have inlets 1 m or 2 m above the shelter roof, interpreting this guidance differently; if shelter roof wind turbulence mixes elevated O3 down to a reactive roof surface, a 1 m spacing may benefit more and be equivalent to a 1 m inlet height above a shelter roof “ground level”. 1220 L Street, NW • Washington, DC 20005-4070 • www.api.org