---
kind: "section"
citation: "40 C.F.R. § 1065.270"
title: "40"
number: "1065.270"
heading: "Chemiluminescent NO X analyzer."
url: "https://uscodex.org/cfr/40/1065.270"
---

# §1065.270. Chemiluminescent NO X analyzer.

- (a) **Application.** You may use a chemiluminescent detector (CLD) to measure NOX concentration in raw or diluted exhaust for batch or continuous sampling. We generally accept a CLD for NOX measurement, even though it measures only NO and NO2, when coupled with an NO2-to-NO converter, since conventional engines and aftertreatment systems do not emit significant amounts of NOX species other than NO and NO2. Measure other NOX species if required by the standard-setting part. While you may also use other instruments to measure NOX, as described in [§ 1065.272](/cfr/40/1065.272.md), use a reference procedure based on a chemiluminescent detector for comparison with any proposed alternate measurement procedure under [§ 1065.10](/cfr/40/1065.10.md).
- (b) **Component requirements.** We recommend that you use a CLD that meets the specifications in Table 1 of [§ 1065.205](/cfr/40/1065.205.md). Note that your CLD-based system must meet the quench verification in [§ 1065.370](/cfr/40/1065.370.md) and it must also meet the linearity verification in [§ 1065.307](/cfr/40/1065.307.md). You may use a heated or unheated CLD, and you may use a CLD that operates at atmospheric pressure or under a vacuum.
- (c) **NO—** 2-to-NO converter. Place upstream of the CLD an internal or external NO2-to-NO converter that meets the verification in [§ 1065.378](/cfr/40/1065.378.md). Configure the converter with a bypass line if it is needed to facilitate this verification.
- (d) **Humidity effects.** You must maintain all CLD temperatures to prevent aqueous condensation. If you remove humidity from a sample upstream of a CLD, use one of the following configurations:
  - (1) Connect a CLD downstream of any dryer or chiller that is downstream of an NO2-to-NO converter that meets the verification in [§ 1065.378](/cfr/40/1065.378.md).
  - (2) Connect a CLD downstream of any dryer or thermal chiller that meets the verification in [§ 1065.376](/cfr/40/1065.376.md).
- (e) **Response time.** You may use a heated CLD to improve CLD response time.

## Notes

### Amendments

[70 FR 40516, July 13, 2005, as amended at 73 FR 37300, June 30, 2008; 76 FR 57442, Sept. 15, 2011; 79 FR 23761, Apr. 28, 2014]

### Authority

Authority: 42 U.S.C. 7401-7671q.

### Source

Source: 70 FR 40516, July 13, 2005, unless otherwise noted.

### Amendments

[70 FR 40516, July 13, 2005, as amended at 73 FR 37300, June 30, 2008; 76 FR 57442, Sept. 15, 2011; 79 FR 23761, Apr. 28, 2014]