---
kind: "section"
citation: "40 C.F.R. § 1065.369"
title: "40"
number: "1065.369"
heading: "H 2 O, CO, and CO 2 interference verification for photoacoustic alcohol analyzers."
url: "https://uscodex.org/cfr/40/1065.369"
---

# §1065.369. H 2 O, CO, and CO 2 interference verification for photoacoustic alcohol analyzers.

- (a) **Scope and frequency.** If you measure ethanol or methanol using a photoacoustic analyzer, verify the amount of H2O, CO, and CO2 interference after initial analyzer installation and after major maintenance.
- (b) **Measurement principles.** H2O, CO, and CO2 can positively interfere with a photoacoustic analyzer by causing a response similar to ethanol or methanol. If the photoacoustic analyzer uses compensation algorithms that utilize measurements of other gases to meet this interference verification, a correct result depends on simultaneously conducting these other measurements to test the compensation algorithms during the analyzer interference verification.
- (c) **System requirements.** Photoacoustic analyzers must have combined interference that is within (0.0 ±0.5) µmol/mol. We strongly recommend a lower interference that is within (0.0 ±0.25) µmol/mol.
- (d) **Procedure.** Perform the interference verification by following the procedure in [§ 1065.375(d)](/cfr/40/1065.375.md?p=d), comparing the results to [paragraph (c)](#c) of this section.

## Notes

### Amendments

[79 FR 23770, Apr. 28, 2014, as amended at 89 FR 29801, Apr. 22, 2024]

### Authority

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

### Source

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

### Amendments

[79 FR 23770, Apr. 28, 2014, as amended at 89 FR 29801, Apr. 22, 2024]