CFR > Title 40 - Protection of Environment > CHAPTER I—ENVIRONMENTAL PROTECTION AGENCY > SUBCHAPTER C—AIR PROGRAMS (Parts 50–99) > PART 90—CONTROL OF EMISSIONS FROM NONROAD SPARK-IGNITION ENGINES AT OR BELOW 19 KILOWATTS > SUBPART B—Emission Standards and Certification Provisions (§90.101 to §90.129) > 90.111—Requirement of certification—prohibition of defeat devices.

90.111—Requirement of certification—prohibition of defeat devices.

(a) An engine may not be equipped with a defeat device.
(b) For purposes of this section, “defeat device” means any device, system, or element of design which senses operation outside normal emission test conditions and reduces emission control effectiveness.
(1) Defeat device includes any auxiliary emission control device (AECD) that reduces the effectiveness of the emission control system under conditions which may reasonably be expected to be encountered in normal operation and use unless such conditions are included in the test procedure.
(2) Defeat device does not include such items which either operate only during engine starting or are necessary to protect the engine (or vehicle in which it is installed) against damage or accident during its operation.