What is Inspection and Maintenance?
Inspection and Maintenance (I/M) 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 can only retain this low-pollution profile if the emission controls and engine are functioning properly. I/M is designed to ensure that vehicles stay clean in actual customer use. Through periodic vehicle checks and required repairs for vehicles that fail the test, I/M encourages proper vehicle maintenance and discourages tampering with emission control devices.

Why is I/M Needed?

Motor vehicle manufacturers have been required to meet increasingly stringent new vehicle pollution standards. But vehicles that are poorly maintained or that have malfunctioning emission controls often exceed those standards. Even minor malfunctions can increase emissions while major malfunctions can cause emissions to skyrocket. The average car on the road emits three to four times more pollution than standards allow for new cars.

The percentage of dirty vehicles increases with age. Roughly 30% of five-year-old cars emit excessive pollution. At seven years old, the average age of passenger cars in the United States, 55% of vehicles are high emitters. Overall, 10% to 30% of vehicles cause the bulk of the problem.

Unfortunately, it is not always obvious which vehicles fall into this category, as the emissions themselves may not be noticeable and emission control malfunctions do not necessarily affect vehicle driveability. Effective I/M programs can identify these problem vehicles and assure their repair.

I/M and Air Quality

Drivers may not think of their own vehicles as pollution sources, but cars and trucks collectively are the single greatest contributor in this country to carbon monoxide pollution and to ground-level ozone, the major component of smog. In typical polluted cities, vehicles contribute between 35% and 70% of ozone-forming emissions and 90% 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.

Substantial reductions in vehicle emissions are essential in cities struggling to achieve clean air. Depending on the sophistication of the program, I/M can reduce vehicle-related hydrocarbon and carbon monoxide emissions by 5% to more than 30%. A comprehensive I/M program can also yield reductions in nitrogen oxide emissions of up to 10%.

EPA oversees a number of programs designed to limit vehicle emissions, including requirements for cleaner vehicles, cleaner fuels, and cleaner transportation alternatives. Still, a well-designed I/M program remains the single most effective and cost-effective way to achieve major reductions in vehicle pollution.

What’s Involved in an I/M Test?

States design and operate I/M programs in accordance with national policy set by EPA. In some states, inspections take place at government or privately-run inspection stations that do not perform vehicle repairs. Other states license service stations and repair shops to do inspections. Most states require annual checks.

Two basic types of tests are performed in I/M programs. The first is a test of emissions from the tailpipe (exhaust emissions). A probe is inserted into the tailpipe while the vehicle is idling or while the engine is being revved to 2500 rpm. Emissions analyzers then measure pollution levels in the exhaust. The second procedure involves a check to ensure that critical emission control components are present and operational. Cars that fail because of dirty exhaust or faulty emission controls must be repaired and re-inspected.

The cost to drivers for an I/M test varies from state to state and ranges from $5 in Arizona to $44 in California. The average test costs $8 in states with -inspection-only programs and $18 in states where repair shops perform inspections.

Repair costs also vary considerably, depending upon the cause of failure. EPA estimates the average bill nationwide to be about $50 to $70 per vehicle that fails the test. The cost of some repairs is covered under emission performance or defect warranties required by the Clean Air Act or under other manufacturer warranties.

States consider vehicle design in setting the pass-fail cutoff for I/M tests. Older vehicles are not held to the same standard as newer models with more sophisticated emission controls. In addition, many states waive repair requirements if the cost exceeds a predetermined limit.

I/M: What’s on the Horizon?

The 1990 Clean Air Act expands the scope of I/M as it currently exists. Many cities will need to start new I/M programs over the next several years and some cities that already require I/M testing will have to institute more comprehensive emission checks. Specifically, the new law calls for either basic or “enhanced” I/M programs in 154 areas, depending on the severity of pollution.

Basic programs will likely resemble those in place today with a simple emissions test and check of emission control devices. “Enhanced” programs will involve more comprehensive and sophisticated emission testing and functional checks. For example, in addition to exhaust from the tailpipe, these programs will address evaporative emissions, an increasingly important aspect of the hydrocarbon pollution problem. The enhanced I/M provisions prohibit stations that conduct I/M tests from performing vehicle repairs and also allows states to take steps such as tightening enforcement procedures to increase the overall effectiveness of their program.

Will New Technologies Eliminate the Need for I/M?

No, but emerging technologies may someday complement I/M programs:

For Further Information:

To learn more about I/M programs in your area, contact your EPA regional office (addresses listed below), or the motor vehicle or environmental agency in your state.

Region 1 – CT, MA, ME, NH, RI, VT
U.S. Environmental Protection Agency
John F. Kennedy Federal Building
Boston, MA 02203

Region 2 – NJ, NY
U.S. Environmental Protection Agency
Air Programs Branch
26 Federal Plaza, Room 1034A
New York, NY 10278

Region 3 – DE, DC, MD, PA, VA, WV
U.S. Environmental Protection Agency
841 Chestnut Building
Philadelphia, PA 19107

Region 4 – AL, FL, GA, KY, MS, NC, SC, TN
U.S. Environmental Protection Agency
345 Courtland Street, N. E.
Atlanta, CA 30365

Region 5 – IL, IN, NU, MN, OH, WI
U.S. Environmental Protection Agency
Air and Radiation Division (5AD26)
Metcalf Federal Building
77 West Jackson
Chicago, Illinois 60604

Region 6 – AR, LA, NM, OK, TX
U.S. Environmental Protection Agency
First Interstate Bank Tower at Fountain Place
1445 Ross Avenue, Suite # 1200
Dallas, TX 75202-2733

Region 7 – IA, KS, MO, NE
U.S. Environmental Protection Agency
726 Minnesota Avenue
Kansas City, KS 66101

Region 8 – CO, MT, ND, SD, UT, WY
U.S. Environmental Protection Agency
999 18th Street
Denver, CO 80202

Region 9 – AZ, CA, HI, NV
U.S. Environmental Protection Agency
75 Hawthorne Street
San Francisco, CA 94105

Region 10 – AK, ID, OR, WA
U.S. Environmental Protection Agency
1200 Sixth Avenue
Seattle, WA 98101

Direct questions about I/M policy to the Emissions Planning and Strategies Division of the EPA National Vehicle and Fuel Emissions Laboratory, 2565 Plymouth Road, Ann Arbor, MI 48105

Direct questions about warranty coverage of emission control components to the Office of Mobile Sources Field Operations and Support Division, LIS EPA (64061), 401 M St. SW, Washington, DC 20460, or call 202-260-2633.


Operating Not Operating Total
States 35 3 38
Basic Urban Areas 75 24 99
Enhanced Areas
Urbanized Areas 17 1 18
Metropolitan Statistical Areas 17 1 18
Enhanced Subtotal 54 29 83
Total Cities
(MSAs & Urban Areas)
131 51 182



Currently Operating **

Allentown-Bethlehem, PA-NJ MSA
Atlanta, GA
Atlantic City, NJ MSA
Bakersfield, CA
Baltimore. MD MSA
Baton Rouge, LA
Bergen-Passaic, NJ PMSA
Boston, MA PMSA
Bridgeport-Milford, CT PMSA
Brockton, MA PMSA
Chicago, IL-NW Indiana
Danbury, CT PMSA
Denver, CO
El Paso, TX-NM
Fall River, MA-RI PMSA
Fitchburg-Leominster, MA MSA
Fresno, CA
Hartford, CT PMSA
Houston, TX
Jersey City, NJ PMSA
Las Vegas, NV
Lawrence-Haverhill, NM-NH PMSA
Los Angeles, CA
Lowell, MA-NH PMSA
Middlesex-Somerset-Hunterdon, NJ PMSA
Milwaukee, WI
Monmouth-Ocean, NJ PMSA
Nashua, NH PMSA
Nassau-Suffolk, NY PMSA
Newark, NJ PMSA
New Bedford, MA MSA
New Britain, C7 PMSA
New Haven-Meriden, CT’MSA
New London-Norwich, CT-RI MSA
New York, NY PMSA
Norwalk, CT PMSA
Oxnard-Ventura, CA
Philadelphia, PA-NJ PMSA
Pittsburgh, PA PMSA
Pawtucket-Woonsocket-Attleboro, RI-NM PMSA
Riverside-San Bemadino, CA
Sacramento, CA
Salem-Gloucester, MA MSA
San Diego, CA
Seattle, WA
Spokane, WA
Springfield, MA MSA
Stamford, CT PMSA
Trenton, NJ PMSA
Vineland-Millville-Bridgeton, NJ PMSA
Washington, DC-MD-VA MSA
Waterbury, CI’MSA
Wilmington, DE-NJ-MD PMSA
Worcester, MA MSA

Not Operating

Albany-Schenectady-Troy, NY MSA
Altoona, PA MSA
Binghamton, NY MSA
Buffalo, NY PMSA
Burlington, VT MSA
Erie, PA MSA
Glen Falls, NY MSA
Hagerstown, MD MSA
Harrisburg-Lebanon-Carlisle, PA MSA
Jamestown-Dunkirk, NY MSA
Johnstown, PA MSA Lancaster, PA MSA
Lancaster, PA MSA
Manchester, NH MSA
Niagara Falls, NY PMSA
Orange County, NY PMSA
Portland, ME MSA
Portsmouth-Dover Rochester, NH-ME MSA
Poughkeepsie, NY MSA
Providence, RI PMSA
Reading, PA MSA
Rochester, NY MSA
Scranton-Wilkes Barre, PA MSA
Sharon, PA MSA
State College, PA MSA
Syracuse, NY MSA
Tacoma, WA
Utica-Rome, NY MSA
Williamsport, PA MSA
York, PA MSA


Currently Operating

Albuquerque, NM
Alton, IL
Anchorage, AK
Antioch-Pittsburg, CA
Aurora, IL
Boise, ID
Boulder, CO
Bristol, CT
Charlotte, NC
Cincinnati, OH-KY
Chico, CA
Cleveland, OH
Colorado Springs, CO
Dallas-Ft. Worth, TX
Davis, CA
Detroit, NU
Durham, NC
Elgin, IL
Fairbanks, AK
Fort Collins, CO
Fort Lauderdale-Hollywood-Pompano Beach, FL
Gastonia, NC
Greeley, CO
Greensboro, NC
Hamilton, OH
Hemet-San Jacinto, CA
Hesperia-Apple Valley-Victorville, CA
High Point, NC
Indio-Coachella, CA
Jacksonville, FL
Joliet, IL
Kenosha, WI
Lancaster-Palmdale, CA
Lodi, CA
Lompoc, CA
Lorain-Elyria, OH
Louisville, KY-IN
Medford, OR
Memphis, TN-AR-MS
Merced, CA
Miami-Hialeah, FL
Middletown, OH
Minneapolis-St.Paul, NV
Modesto, CA
Napa, CA
Nashville, TN
Ogden, Lrl’
Palm Springs, CA
Phoenix, AZ
Portland-Vancouver, OR-WA
Provo-Orem, UT
Racine, WI
Raleigh, NC
Reno, NV
Round Lake Beach-McHenry,IL-WI
Salinas, CA
Salt Lake City, UT
San Francisco-Oakland, CA
San Jose, CA
San Luis Obispo, CA
Santa Barbara, CA
Santa Cruz, CA
Santa Maria, CA
Santa Rosa, CA
Seaside-Monterey, CA
SimiValley, CA
St. Louis, MO-IL
Stockton, CA
Tampa-St. Petersburg-Clearwater, FL
Tucson, AZ
Vacaville, CA
Visalia, CA
West Palm Beach-Boca Raton-Delray Beach, FL
Winston Salem, NC

Not Operating

Akron, OH
Ann Arbor, NU
Beaumont, TX
Charleston, @
Crystal Lake, IL
Dayton, OH
Denton, TX
Galveston, TX
Grand Rapids, NU
Holland, NU
Huntington-Ashland, WV-KY-OH
Lewiston-Auburn, ME
Lewisville, TX
Muskegon, NU
Newport, RI
Parkersburg, WV-OH
Petersburg-Colonial Heights, VA
Port-Arthur, TX
Port Huron, MI
Richmond, VA
Sheboygan, WI
Springfield, OH
Texas City, TX
Toledo, OH-NU

* This list shows Metropolitan Statistical Areas (MSAS) and Primary Metropolitan Statistical Areas (PMSAS) in the North Eastern Ozone Transport Region and urbanized areas in the rest of the country.

** These areas are currently operating I/M programs but are not necessarily meeting enhanced I/M requirements.

List Updated 5-19-93

Source: US EPA

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