Section 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) [MICRO]mol/mol. We strongly recommend a lower interference that is within (0.0 ±0.25) [MICRO]mol/mol.(d)Procedure. Perform the interference verification by following the procedure in § 1065.375(d) , comparing the results to paragraph (c) of this section. 79 FR 23770 , Apr. 28, 2014, as amended at 89 FR 29801 , Apr. 22, 2024 79 FR 23770 , 4/28/2014, as amended at 89 FR 29801 , 6/21/2024