Nitrogen dioxide (NO2) is one of a group of highly reactive gases known as "oxides of nitrogen" or "nitrogen oxides (NOx)." Other nitrogen oxides include nitrous oxide (N2O) and nitric oxide (NO). The National Ambient Air Quality Standard covers NO2 which forms from the emissions of cars, trucks and buses, power plants, and off-road equipment. In addition to contributing to the formation of ground-level ozone and fine particulate pollution, NO2 is linked with a number of adverse health effects on the respiratory system. There are two federal standards for nitrogen dioxide. Oklahoma is in attainment with both standards.

Pollutant Primary/
Level Form
Nitrogen Dioxide primary 1-hour 100 ppb 98th percentile, averaged over 3 years
primary and secondary Annual 53 ppb Annual Mean

NO2 Monitoring Sites

The division monitors nitrogen dioxide at three sites in Oklahoma City and one site in Tulsa. All NO2 measurements are made using an approved chemiluminescent method. Monitors report every hour and those values are used to determine compliance. All four sites presently meet the NO2 standard. Current data may be accessed here.

2013 NO2 Data

DEQ expects NO2 concentrations will continue to decrease in the future as a result of a number of mobile source regulations that are taking effect. New federal standards for light-duty vehicles began phasing in during 2004, and new NOx standards for heavy-duty engines were phased in between 2007 and 2010 model years. Current air quality monitoring data does not yet reflect the benefit of vehicles that meet these strict NOx standards. The benefit of these reductions are even more significant when considering the role of NOx as a precursor to ozone.

2013 1-hour NO2 Values2013 CO Values vs. Arithmetic Mean

*To attain this standard, the 3-year average of the 98th percentile of the daily maximum 1-hour average at each monitor within an area must not exceed 100 ppb (effective January 22, 2010).

**The Yukon site was added to the NO2 network in early March of 2013. The data gathered at the new location cannot be compared to the standard until 3 years of complete data are collected. This chart reflects only that of 2013.