§ 1065.350 H2O interference verification for CO2 NDIR analyzers.
(a) Scope and frequency. If you measure CO2 using an NDIR analyzer, verify the amount of H2O interference after initial analyzer installation and after major maintenance.
(b) Measurement principles. H2O can interfere with an NDIR analyzer's response to CO2.
If the NDIR analyzer uses compensation algorithms that utilize measurements of other gases to meet this interference verification, simultaneously conduct these other measurements to test the compensation algorithms during the analyzer interference verification.
(c) System requirements. A CO2 NDIR analyzer must have an H2O interference that is within (0.0 ±0.4) mmol/mol, though we strongly recommend a lower interference that is within (0.0 ±0.2) mmol/mol.
(d) Procedure. Perform the interference verification as follows:
(1) Start, operate, zero, and span the CO2 NDIR analyzer as you would before an emission test. If the sample is passed through a dryer during emission testing, you may run this verification test with the dryer if it meets the requirements of § 1065.342. Operate the dryer at the same conditions as you will for an emission test. You may also run this verification test without the sample dryer.