Vehicles registered in 13 out of Maryland's 18 counties and the city of Baltimore are required to undergo biennial emissions testing.
Counties: Anne Arundel, Baltimore, Calvert, Carroll, Cecil, Charles, Frederick, Harford, Howard, Montgomery, Prince George's, Queen Anne's, and Washington
OBD testing is performed on vehicles model year 1996 and newer and an idle tailpipe and gas cap test is administered on model year 1977-1995 vehicles.
Diesel Vehicles:
Diesel vehicles are not tested for emissions.
Exemptions:
- 1995 or older under 8500 Gross Vehicle Weight
- Vehicles weighing more than 26,000 pounds gross vehicle weight
- Vehicles registered as a farm truck, farm truck tractor or farm area vehicle
- Historic or Antique vehicles
- New vehicles and qualified hybrids for the first 36 months after titling and registration
- Vehicles registered to senior citizens over 70 or vehicles registered with hard metal disable tags and who drive 5,000 miles per year or less (if co-owned, both owners must qualify for the waiver) can apply for a waiver for the balance of the two year cycle. Mileage must be recertified every two years to continue to received the waiver
- Vehicles registered as a Class N street rod vehicle
For more information visit:
Maryland Transportation Code
§ 22-402. Mufflers; prevention of noise; discharge of smoke; maximum period of idling
(a) Mufflers. -- Every motor vehicle with an internal combustion engine shall be equipped with an exhaust muffler system in good working order and in constant operation to prevent excessive or unusual noise, and no person may use a muffler cutout, bypass, or similar device on a motor vehicle on a highway. Noise levels in excess of those adopted by the Administrator under § 22-601 of this title are excessive.
(b) Prevention of noise. -- A person may not use on the exhaust or "tail pipe" of a motor vehicle any extension or other device to cause excessive or unusual noise.
(c) Discharge of smoke; maximum period of idling. --
(1) No motor vehicle may be operated, nor may the owner or lessee of a motor vehicle permit it to be operated, on any highway in this State unless the engine power and exhaust mechanism is equipped, adjusted, and operated to prevent:
(i) The discharge of clearly visible smoke (comparable to smoke equal to or darker in shade than that designated as No. 1 of the Ringelmann Chart as published by the U.S. Bureau of Mines) in the exhaust emissions within the proximity of the exhaust outlet for more than 10 consecutive seconds; and
(ii) The discharge of smoke from any other part of the engine in such amounts and of such opacity as to partially obscure persons or objects from view.
(2) In this subsection, "smoke" means small gasborne and airborne particles, exclusive of water vapor, from a process of combustion in sufficient numbers to be observable.
(5) This subsection does not apply to Class L (historic) vehicles.
(d) "Muffler" defined. -- In this section, "muffler" means a device designed for and effective in reducing noise while permitting the flow of gases.
(e) Leakproof construction. -- All mufflers and exhaust pipes carrying exhaust gases from the motor shall be of leakproof construction.
§ 22-609. Modification of exhaust system
(a) Modification that increases sound prohibited. -- A person may not modify the exhaust system or any other noise abatement device of a motor vehicle driven or to be driven on any highway in this State in such a way that the noise emitted by the vehicle exceeds that emitted by the vehicle as originally manufactured.
(b) Operation of improperly modified vehicle prohibited. -- A person may not drive on any highway in this State a motor vehicle with an exhaust system or noise abatement device modified in a way prohibited by subsection (a) of this section.
Historic
Available for vehicles that are at least 20 years old that have not been substantially altered, remodeled, or remanufactured from their original construction. Historic vehicles cannot be used for general daily transportation. Only required to display a single rear plate.
Street Rod
Available for vehicles that are at least 25 years old that have been substantially altered from the manufacturer's original design. Street rods cannot be used for general daily transportation. Only required to display a single rear plate.
Special Vintage Reproduction Plate
Reproduction of Maryland's 1910 plate available to most vehicles, including historic vehicles and street rods.
YOM
Vehicles registered as "Historic" or "Street Rod" may display YOM plates with DMV approval. The street rod or historic plates must be carried within the vehicle at all times.