§ 1066.420 Test preparation.

(a) Follow the procedures for PM sample preconditioning and tare weighing as described in 40 CFR 1065.590 if you need to measure PM emissions.

(b) Minimize the effect of nonmethane hydrocarbon contamination in the hydrocarbon sampling system for vehicles with compression-ignition engines as follows:

(1) For vehicles at or below 14,000 pounds GVWR, account for contamination using one of the following methods:

(i) Introduce zero and span gas during analyzer calibration using one of the following methods, noting that the hydrocarbon analyzer flow rate and pressure during zero and span calibration (and background bag reading) must be exactly the same as that used during testing to minimize measurement errors:

(A) Close off the hydrocarbon sampling system sample probe and introduce gases downstream of the probe making sure that you do not pressurize the system.

(B) Introduce zero and span gas directly at the hydrocarbon sampling system probe at a flow rate greater than 125% of the hydrocarbon analyzer flow rate allowing some gas to exit probe inlet.

(ii) Perform the contamination verification in paragraph (b)(2) of this section, except use 0.5 µmol/mol in 40 CFR 1065.520(f)(8)(iii).

(2) For vehicles above 14,000 pounds GVWR, verify the amount of nonmethane hydrocarbon contamination as described in 40 CFR 1065.520(f).