CFR > Title 40 - Protection of Environment > CHAPTER I—ENVIRONMENTAL PROTECTION AGENCY > SUBCHAPTER C—AIR PROGRAMS (Parts 50–99) > PART 86—CONTROL OF EMISSIONS FROM NEW AND IN-USE HIGHWAY VEHICLES AND ENGINES > SUBPART D—Emission Regulations for New Gasoline-Fueled and Diesel-Fueled Heavy-Duty Engines; Gaseous Exhaust Test Procedures (§86.301-79 to §86.348-79) > 86.346-79—Alternative NO X measurement technique.

86.346-79—Alternative NO X measurement technique.

(a) Oxides of nitrogen (NOX) may be measured with the following “alternative instrumentation” for both Diesel and gasoline-fueled engines. The “alternative instrumentation” shall consist of:
(1) A heated sample line maintained above the dew point:
(2) An NO2 to NO converter obtaining a sample directly from the heated sample line; and
(3) A combination per 40 CFR 86.777 or CFR 86.977, whichever is applicable of a water trap, dryer, flow controls, and an NO NDIR analyzer obtaining a sample from the converter.
(b) The provisions of 40 CFR 86 subpart D shall apply to the “alternative instrumentation”, where applicable, with the following exceptions:
(1) Analyzer specifications found in §§ 86.315, 86.321, and 86.322 do not apply to the “alternative instrumentation”.
(2) For the purposes of this section, the full-scale value specified in § 86.338 (a)(1) shall be 1,500 ppm for Diesel engines and 2,500 ppm for gasoline-fueled engines.
(c) The “alternative instrumentation” shall be calibrated per § 86.330.
(d) The NO NDIR analyzer shall meet the performance and interference specifications contained in 40 CFR 86.777 or CFR 86.977, whichever is applicable.
(e) The operation of the dryer shall follow good engineering practice such that the test results are not altered. Proper preconditioning of the dryer is allowed.