---
kind: "section"
citation: "40 C.F.R. § 1065.366"
title: "40"
number: "1065.366"
heading: "Interference verification for FTIR analyzers."
url: "https://uscodex.org/cfr/40/1065.366"
---

# §1065.366. Interference verification for FTIR analyzers.

- (a) **Scope and frequency.** If you measure CH4, C2H6, NMHC, or NMNEHC using an FTIR analyzer, verify the amount of interference after initial analyzer installation and after major maintenance.
- (b) **Measurement principles.** Certain species can interfere with analyzers by causing a response similar to the target analyte. If the 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.** An FTIR analyzer must have combined interference that is within ±2% of the flow-weighted mean concentration of CH4, NMHC, or NMNEHC expected at the standard, though we strongly recommend a lower interference that is within ±1%.
- (d) **Procedure.** Perform the interference verification for an FTIR analyzer using the same procedure that applies for N2O analyzers in [§ 1065.375(d)](/cfr/40/1065.375.md?p=d).

## Notes

### Amendments

[81 FR 74168, Oct. 25, 2016, 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

[81 FR 74168, Oct. 25, 2016, as amended at 89 FR 29801, Apr. 22, 2024]