StacksVerified U.S. regulatory reference

40 CFR §1065.274

Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
  1. (a)Application. You may use a zirconia oxide (ZrO2) analyzer to measure NOX in raw exhaust for field-testing engines.
  2. (b)Component requirements. We recommend that you use a ZrO2 analyzer that meets the specifications in Table 1 of § 1065.205. Note that your ZrO2-based system must meet the linearity verification in § 1065.307.
  3. (c)Species measured. The ZrO2-based system must be able to measure and report NO and NO2 together as NOX. If the ZrO2-based system cannot measure all of the NO2, you may develop and apply correction factors based on good engineering judgment to account for this deficiency.
  4. (d)Interference. You must account for NH3 interference with the NOX measurement.