40 CFR § 1065.274 - Zirconium dioxide (ZrO) NO analyzer.

---
identifier: "/us/cfr/t40/s1065.274"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 1065.274 - Zirconium dioxide (ZrO) NO analyzer."
title_number: 40
title_name: "Protection of Environment"
section_number: "1065.274"
section_name: "Zirconium dioxide (ZrO) NO analyzer."
chapter_name: "ENVIRONMENTAL PROTECTION AGENCY"
subchapter_number: "U"
subchapter_name: "AIR POLLUTION CONTROLS"
part_number: "1065"
part_name: "ENGINE-TESTING PROCEDURES"
positive_law: false
currency: "2026-04-05"
last_updated: "2026-04-05"
format_version: "1.1.0"
generator: "[email protected]"
authority: "42 U.S.C. 7401-7671q."
regulatory_source: "70 FR 40516, July 13, 2005, unless otherwise noted."
cfr_part: "1065"
---


# 1065.274 Zirconium dioxide (ZrO) NO analyzer.

(a) *Application.* You may use a zirconia oxide (ZrO<sub>2</sub>) analyzer to measure NO<sub>X</sub> in raw exhaust for field-testing engines.

(b) *Component requirements.* We recommend that you use a ZrO<sub>2</sub> analyzer that meets the specifications in Table 1 of § 1065.205. Note that your ZrO<sub>2</sub>-based system must meet the linearity verification in § 1065.307.

(c) *Species measured.* The ZrO<sub>2</sub>-based system must be able to measure and report NO and NO<sub>2</sub> together as NO<sub>X</sub>. If the ZrO<sub>2</sub>-based system cannot measure all of the NO<sub>2</sub>, you may develop and apply correction factors based on good engineering judgment to account for this deficiency.

(d) *Interference.* You must account for NH<sub>3</sub> interference with the NO<sub>X</sub> measurement.

[88 FR 4673, Jan. 24, 2023]