Vehicle Emissions Inspection and Maintenance (I/M)

What is Inspection and Maintenance?

The Inspection and Maintenance (I/M) program is a way to check whether the emission control system on a vehicle is working correctly. All new passenger cars and trucks sold in the United States today must meet stringent pollution standards, but they remain low-polluters if the emission controls and the engine are both functioning properly. I/M is a state-operated program designed to ensure that vehicles stay clean after they leave the factory and are in-use by the driving public. Through periodic emissions performance checks and repairs for those vehicles that fail emissions tests, I/M encourages proper vehicle maintenance and discourages tampering with emission control devices.

Why is Emissions Testing Needed in Region 3?

Motor vehicle manufacturers have been required to meet increasingly stringent new vehicle air pollution standards. But vehicles that are poorly maintained or that have malfunctioning emission controls often emit pollution at levels exceeding these standards. Even seemingly minor malfunctions can cause increased emissions. Major malfunctions can cause emissions to skyrocket by hundreds of times beyond federal vehicle standards. Even though cars having malfunctioning emissions controls comprise a small portion of the fleet, they can have dramatically higher emissions.

Drivers typically don't think of their own vehicle as a significant source of air pollution, but cars and trucks collectively are the single greatest contributor in this country to carbon monoxide pollution and to ground-level ozone, or smog. In our more polluted cities, vehicles contribute between 35 and 70 percent of ozone-forming emissions and 90 percent or more of carbon monoxide emissions. Ambient concentrations of one or both of these pollutants exceed national air quality standards in virtually every major urban area of the country, including the Philadelphia, Baltimore, and Washington, DC metropolitan areas.

Substantial reductions in vehicle emissions are essential in our cities' struggle to achieve clean air. I/M programs can significantly reduce vehicle-related ozone-forming and carbon monoxide emissions. A comprehensive I/M program can also yield substantial reductions in nitrogen oxide emissions.

What is on the Horizon for I/M in Region 3?

On-board diagnostic (OBD) system checks are now becoming a major element of emissions testing. New second generation OBD systems were added to cars beginning in the 1994 model year. These advanced OBD systems use the vehicle's on-board computer to monitor emissions devices and engine control systems that can impact emissions performance. If the system detects a malfunction, the computer stores a code that aids in diagnosis of the problem and triggers a dashboard indicator light alerting the motorist of a problem.

By 2001, states began incorporating on-board diagnostic (OBD) system checks into the emissions test process. A computer checks for any stored trouble codes, the dashboard malfunction light is also checked. However, you don't need to wait for your emissions test to respond to an illuminated dashboard malfunction light. If you see the light, have your vehicle checked for problems as soon as possible and you can do your part to reduce air pollution before it deteriorates.

Where is I/M being performed in Region 3?

This map includes the I/M counties in the Mid-Atlantic region. For additional information regarding specifics of the I/M program for your county go to the respective state information page...