Section 243.124  Nitrogen Dioxide

a)         Standard. The ambient air quality standard for nitrogen dioxide is an annual arithmetic mean concentration of 100 micrograms per cubic meter (0.05 ppm).

b)         Measurement Method.  For determining conformance with the nitrogen dioxide air quality standard, nitrogen dioxide shall be measured by the colorimetric method as described in 36 Fed. Reg. 22,396, November 25, 1971, or by an equivalent method approved by the Agency.