Clean Air Act Compliance Glossary.

The federal statute under which EPA regulates vehicle and engine emissions.

The Clean Air Act is the principal federal law governing air pollution in the United States, codified at 42 U.S.C. §§ 7401–7671q. Title II of the Act (42 U.S.C. §§ 7521–7590) regulates emissions from motor vehicles and motor vehicle engines, including manufacturer certification requirements, the prohibition on tampering with emission controls, and the prohibition on the manufacture and sale of defeat devices. The U.S. Environmental Protection Agency administers Title II's implementing regulations at 40 C.F.R. Parts 85, 86, 88–94, 600, and 1033–1068.

Any device or component that bypasses, defeats, or renders inoperative an emission control device or system.

A defeat device is any auxiliary emission control device, AECD, or aftermarket part the principal effect of which is to bypass, defeat, or render inoperative any device or element of design installed on a motor vehicle to comply with the Clean Air Act's emission standards. The manufacture, sale, and installation of defeat devices for use in motor vehicles is prohibited by 42 U.S.C. § 7522(a)(3)(B). This prohibition applies to manufacturers, distributors, retailers, and installers — not only to original equipment manufacturers. The statutory maximum civil penalty was $4,876 per defeat device sale or installation at the time most aftermarket settlements resolved.

Removing or rendering inoperative an emission control device installed by the manufacturer.

Tampering refers to the removal or rendering inoperative of any emission control device or system installed on a motor vehicle for the purpose of complying with EPA emission standards. Tampering is prohibited under 42 U.S.C. § 7522(a)(3)(A) for manufacturers and dealers, and under § 7522(a)(3)(C) for any person — including vehicle owners and fleet operators — engaged in the business of repair, service, or sale of vehicles or engines.

California's certification number for an aftermarket part approved for street use on California-registered vehicles.

A CARB Executive Order is the certification number issued by the California Air Resources Board to an aftermarket part that has been tested and approved as legal for street use on a California-registered vehicle. CARB EO numbers follow the format "D-XXX-NN" or "D-XXX-N." Parts without a current CARB EO are limited to off-road or competition use only on California-registered vehicles. Because seventeen Section 177 states have adopted California vehicle emission standards, a CARB EO is also generally required for street use in those jurisdictions.

The seventeen states that have adopted California vehicle emission standards in lieu of less-strict federal standards.

Section 177 of the federal Clean Air Act (42 U.S.C. § 7507) authorizes any state with a state implementation plan to adopt California vehicle emission standards rather than the federal standards. Seventeen jurisdictions have done so: California (origin), Colorado, Connecticut, Delaware, Maine, Maryland, Massachusetts, Minnesota, New Jersey, New Mexico, New York, Oregon, Pennsylvania, Rhode Island, Vermont, Virginia, Washington. The practical effect for aftermarket retailers is that any part requiring a CARB Executive Order in California also requires it in these states.

EPA's certification that a vehicle or engine family meets applicable emission standards before sale.

A Certificate of Conformity is the EPA-issued certification that a manufacturer's vehicle or engine family meets applicable Clean Air Act emission standards. Every new motor vehicle and motor vehicle engine introduced into commerce in the United States must be covered by a valid Certificate of Conformity. Manufacturer enforcement cases frequently allege the introduction of uncertified engines into commerce, the submission of false or misleading certification data, or failure to comply with the reporting and recordkeeping obligations attached to certified engine families.

A signed customer acknowledgment that a part is purchased for off-road or competition use only, not for installation on a street-driven vehicle.

An off-road use declaration is a signed customer acknowledgment, typically captured at point of sale, that the purchased component is intended for off-road, race, or closed-course competition use only. Off-road use declarations are the principal documentary evidence shops rely on when selling parts that are not street-legal under federal or state emission standards. The declaration must be genuine — a buyer who installs an off-road-only part on a street-driven vehicle does not retroactively legitimize the sale, but a properly executed declaration substantially affects the regulatory posture available to the shop in the event of subsequent enforcement contact.

The removal or rendering inoperative of a diesel particulate filter on a diesel engine.

A DPF delete is the physical removal or electronic disabling of a diesel particulate filter, the emission control device that traps particulate matter from a diesel engine's exhaust stream. DPF deletes — whether performed via hardware removal, ECU tune, or both — are tampering under 42 U.S.C. § 7522(a)(3)(A) when performed on a vehicle subject to federal emission standards. DPF delete kits and tunes are defeat devices under § 7522(a)(3)(B), and the manufacture, sale, and installation are prohibited.

The removal or rendering inoperative of an exhaust gas recirculation system.

An EGR delete is the physical removal or electronic disabling of an exhaust gas recirculation system, the emission control device that routes a portion of an engine's exhaust gas back through the intake to reduce nitrogen oxide formation. EGR deletes are tampering and the kits/tunes that perform them are defeat devices under the Clean Air Act.

The removal or rendering inoperative of a diesel exhaust fluid (selective catalytic reduction) system.

A DEF delete is the physical removal or electronic disabling of a diesel exhaust fluid (DEF) injection system or its associated selective catalytic reduction (SCR) catalyst, the emission control system that reduces nitrogen oxides in modern diesel engines. DEF deletes are tampering and the products that perform them are defeat devices under the Clean Air Act.

An exhaust component that removes or replaces the factory catalytic converter.

A catless exhaust is any exhaust component — downpipe, mid-pipe, or full system — that removes the factory catalytic converter or replaces it with a non-catalyzed pipe (sometimes marketed as a "test pipe" or "resonator delete"). Catless components installed on street-driven vehicles violate the tampering prohibition. Sale of catless components is permissible only where the buyer has executed an off-road use declaration confirming the part will be used on a non-street-driven vehicle. Several recent EPA enforcement cases have specifically involved catless exhaust manufacturers and retailers.

Federal law that limits a manufacturer's ability to void a warranty solely because an aftermarket part was installed.

The Magnuson-Moss Warranty Act, codified at 15 U.S.C. §§ 2301–2312, governs consumer product warranties. For automotive aftermarket purposes, the Act prohibits a vehicle manufacturer or dealer from voiding the entire factory warranty solely because the consumer installed an aftermarket part. The manufacturer must show that the specific aftermarket part caused the specific failure being claimed. The Act does not protect installation of illegal parts (e.g., defeat devices) — those installations are independently unlawful regardless of warranty consequences.

EPA's internal policy for determining civil penalty amounts in vehicle and engine enforcement cases.

The Mobile Source Civil Penalty Policy is the internal EPA policy that the Office of Enforcement and Compliance Assurance applies to determine the appropriate civil penalty in a vehicle or engine enforcement matter. The Policy considers factors including the gravity of the violation, the violator's economic benefit from non-compliance, the violator's compliance history, ability to pay, and any mitigation. Adoption of a documented compliance program before regulatory contact is a recognized mitigating factor in the calculation.

An internal directive to preserve all records relevant to anticipated or pending litigation.

A litigation hold is an internal directive issued by a business at the moment it knows or reasonably should know of pending or threatened litigation, requiring the preservation of all potentially relevant records. Failure to issue a timely litigation hold can result in sanctions for spoliation of evidence under federal evidentiary rules. EPA enforcement contact is a triggering event. The Compliance Standard issues a Litigation Hold & Records Preservation instrument as part of the regulatory contact response category.

The portion of the Clean Air Act addressing motor vehicle and motor vehicle engine emissions.

Title II of the Clean Air Act (42 U.S.C. §§ 7521–7590) is the portion of the Act that regulates motor vehicle and motor vehicle engine emissions. It includes manufacturer certification requirements (§ 7525), the prohibition on tampering and defeat devices (§ 7522), the civil penalty provisions (§ 7524), and the regulatory authority for off-road and non-road engines.

The California state agency that administers California's vehicle emission standards.

The California Air Resources Board is the California state agency, established under the California Health and Safety Code, that administers California's vehicle and engine emission standards. CARB operates a parallel state authority to the federal EPA, including its own certification program (CARB Executive Orders) and its own enforcement function. CARB's authority extends to seventeen jurisdictions through Section 177 of the federal Clean Air Act.

A formal letter sent in response to initial regulatory contact, before retained counsel issues a substantive response.

An EPA Holding Letter is a brief, formal letter sent in response to initial regulatory contact from the EPA, the California Air Resources Board, or a parallel state authority. The Holding Letter acknowledges receipt of the contact, identifies the responder's relationship to the matter, references retained counsel, and requests a defined extension of time for substantive response. It does not respond to the substance of the contact — that response is the proper province of retained counsel after evidence file review. The Compliance Standard issues a Holding Letter template customized to the member shop.