Section 1065.935 - Emission test sequence for field testing(a) Time the start of field testing as follows:(1) If the standard-setting part requires only hot-stabilized emission measurements, operate the engine in-use until the engine coolant, block, or head absolute temperature is within ±10% of its mean value for the previous 2 min or until an engine thermostat controls engine temperature with coolant or air flow.(2) If the standard-setting part requires hot-start emission measurements, shut down the engine after at least 2 min at the temperature tolerance specified in paragraph (a)(1) of this section. Start the field test within 20 min of engine shutdown.(3) If the standard-setting part requires cold-start emission measurements, proceed to the steps specified in paragraph (b) of this section.(b) Take the following steps before emission sampling begins: (1) For batch sampling, connect clean storage media, such as evacuated bags or tare-weighed PM sample media.(2) Operate the PEMS according to the instrument manufacturer's instructions and using good engineering judgment.(3) Operate PEMS heaters, dilution systems, sample pumps, cooling fans, and the data-collection system.(4) Pre-heat or pre-cool PEMS heat exchangers in the sampling system to within their tolerances for operating temperatures.(5) Allow all other PEMS components such as sample lines, filters, and pumps to stabilize at operating temperature.(6) Verify that no significant vacuum-side leak exists in the PEMS, as described in § 1065.345 .(7) Adjust PEMS flow rates to desired levels, using bypass flow if applicable.(8) Zero and span all PEMS gas analyzers using NIST-traceable gases that meet the specifications of § 1065.750 .(c) Start testing as follows: (1) Before the start of the first test interval, zero or re-zero any PEMS electronic integrating devices, as needed.(2) If the engine is already running and warmed up and starting is not part of field testing, start the field test by simultaneously starting to sample exhaust, record engine and ambient data, and integrate measured values using a PEMS.(3) If engine starting is part of field testing, start field testing by simultaneously starting to sample from the exhaust system, record engine and ambient data, and integrate measured values using a PEMS. Then start the engine.(d) Continue the test as follows: (1) Continue to sample exhaust, record data and integrate measured values throughout normal in-use operation of the engine.(2) Between each test interval, zero or re-zero any electronic integrating devices, and reset batch storage media, as needed.(3) The engine may be stopped and started, but continue to sample emissions throughout the entire field test.(4) Conduct periodic verifications such as zero and span verifications on PEMS gas analyzers and use these to correct for drift according to paragraph (g) of this section. Do not include data recorded during verifications in emission calculations. Conduct the verifications as follows: (i) For PEMS gas analyzers used to determine NTE emission values, perform verifications as recommended by the PEMS manufacturer or as indicated by good engineering judgment.(ii) For PEMS gas analyzers used to determine bin emission values, perform zero verifications at least hourly using purified air. Perform span verification at the end of the shift-day or more frequently as recommended by the PEMS manufacturer or as indicated by good engineering judgment.(5) You may periodically condition and analyze batch samples in-situ, including PM samples; for example you may condition an inertial PM balance substrate if you use an inertial balance to measure PM.(6) You may have personnel monitoring and adjusting the PEMS during a test, or you may operate the PEMS unattended.(e) Stop testing as follows: (1) Continue sampling as needed to get an appropriate amount of emission measurement, according to the standard setting part. If the standard-setting part does not describe when to stop sampling, develop a written protocol before you start testing to establish how you will stop sampling. You may not determine when to stop testing based on emission results.(2) At the end of the field test, allow the sampling systems' response times to elapse and then stop sampling. Stop any integrators and indicate the end of the test cycle on the data-collection medium.(3) You may shut down the engine before or after you stop sampling.(f) For any proportional batch sample, such as a bag sample or PM sample, verify for each test interval whether or not proportional sampling was maintained according to § 1065.545 . Void the sample for any test interval that did not maintain proportional sampling according to § 1065.545 .(g) Take the following steps after emission sampling is complete: (1) As soon as practical after emission sampling, analyze any gaseous batch samples.(2) If you used dilution air, either analyze background samples or assume that background emissions were zero. Refer to § 1065.140 for dilution-air specifications.(3) After quantifying all exhaust gases, record mean analyzer values after stabilizing a zero gas to each analyzer, then record mean analyzer values after stabilizing the span gas to the analyzer. Stabilization may include time to purge an analyzer of any sample gas and any additional time to account for analyzer response. Use these recorded values, including pre-test verifications and any zero verifications during testing, to correct for drift as described in § 1065.550 .(4) Verify PEMS gas analyzers used to determine NTE emission values as follows:(i) Invalidate any data that does not meet the range criteria in § 1065.550 . Note that it is acceptable that analyzers exceed 100% of their ranges when measuring emissions between test intervals, but not during test intervals. You do not have to retest an engine if the range criteria are not met.(ii) Invalidate any data that does not meet the drift criterion in § 1065.550 . For HC, invalidate any data if the difference between the uncorrected and the corrected brake-specific HC emission values are not within ±10% of the uncorrected results or the applicable standard, whichever is greater. For data that does meet the drift criterion, correct those test intervals for drift according to § 1065.672 and use the drift corrected results in emissions calculations.(5) Verify PEMS gas analyzers used to determine bin emission values as follows:(i) Invalidate data from a whole shift-day if more than 1% of recorded 1 Hz data exceeds 100% of the selected gas analyzer range. For analyzer outputs exceeding 100% of range, calculate emission results using the reported value. You must retest an engine if the range criteria are not met.(ii) Invalidate any data for periods in which the CO and CO2 gas analyzers do not meet the drift criterion in § 1065.550 . For HC, invalidate data if the difference between the uncorrected and the corrected brake-specific HC emission values are not within ±10% of the uncorrected results or the applicable standard, whichever is greater. For data that do meet the drift criterion, correct the data for drift according to § 1065.672 and use the drift-corrected results in emissions calculations.(iii) For PEMS NOX analyzers used to determine bin emission values, invalidate data for the engine over the entire shift-day if any data do not meet the following drift limits instead of meeting the drift criteria specified in § 1065.550 : (A) The allowable analyzer zero-drift between successive zero verifications is ±2.5 ppm. The analyzer zero-drift limit over the shift-day is ±10 ppm.(B) The allowable analyzer span-drift limit is ±4% of the measured span value between successive span verifications.(6) Unless you weighed PM in-situ, such as by using an inertial PM balance, place any used PM samples into covered or sealed containers and return them to the PM-stabilization environment and weigh them as described in § 1065.595 . 70 FR 40516 , July 13, 2005, as amended at 73 FR 37345 , June 30, 2008; 88 FR 4688 , Jan. 24, 2023; 89 FR 29826 , Apr. 22, 2024 88 FR 4688 , 3/27/2023; 89 FR 29826 , 6/21/2024