40 CFR 90.118 - Certification procedure
(1) The test engine must be operated with all emission control systems operating properly for a period sufficient to stabilize emissions.
(2) The period sufficient to stabilize emissions may not exceed 12 hours.
(b) No maintenance, other than recommended lubrication and filter changes, may be performed during service accumulation without the Administrator's approval.
(c) Service accumulation is to be performed in a manner using good engineering judgment to ensure that emissions are representative of production engines.
(d) The manufacturer must maintain, and provide to the Administrator if requested, records stating the rationale for selecting a service accumulation period less than 12 hours and records describing the method used to accumulate hours on the test engine(s).
(e) For purposes of establishing whether Phase 2 engines comply with applicable exhaust emission standards or FELs, the test results for each regulated pollutant as measured pursuant to § 90.119 shall be multiplied by the applicable df determined under § 90.104 (g) or (h). The product of the two numbers shall be rounded to the same number of decimal places contained in the applicable standard, and compared against the applicable standard or FEL, as appropriate.