§ 86.140-94 Exhaust sample analysis.
The following sequence shall be performed in conjunction with each series of measurements:
(a) For CO, CO2, CH4, NOX, and for Otto-cycle and methanol-fueled, natural gas-fueled and liquefied petroleum gas-fueled (if non-heated FID option is used) diesel vehicle HC:
(1) Zero the analyzers and obtain a stable zero reading. Recheck after tests.
(2) Introduce span gases and set instrument gains. In order to avoid errors, span and calibrate at the same flow rates used to analyze the test sample. Span gases should have concentrations equal to 75 to 100 percent of full scale. If gain has shifted significantly on the analyzers, check the calibrations. Show actual concentrations on chart.
(3) Check zeroes; repeat the procedure in paragraphs (a) (1) and (2) of this section if required.