Scrub Hub: Why doesn't Indiana have a car emissions inspection program?

Many of us have received the notices for Air Quality Action Days in Indiana — the ones where the state tells us to limit our time and activities outdoors because the air is too unhealthy. Those are the days when the amount of ground level ozone or fine particulate matter has become too high and is unsafe.

One of the main sources for these dangerous pollutants are cars and the exhaust that emanates from them.

That’s why the Clean Air Act established tighter pollution standards for the emissions from cars and trucks in an effort to improve air quality. That’s when car emissions check programs were born.

Still, not every state nor every city has one. And for those that do have such a program, they are not all the same.

The Scrub Hub.
The Scrub Hub.

For this edition of the Scrub Hub, we will be looking at a question we received from a few different readers. More specifically, Alisa and Ruth asked why Indiana doesn’t require yearly car emissions inspections.


The answer, as these science topics often are, is a bit complicated. But we spoke to the state’s environmental regulatory agency to figure out what car emissions look like in Indiana.

Short Answer: Indiana does have a program

Indiana does, in fact, have a car emissions check program. That said, It is only in two of the state’s 92 counties: Lake and Porter counties in Northwest Indiana.

There are seven testing stations across the two counties, and about 230,000 cars are inspected each year through the program, according to the Indiana Department of Environmental Management.

The program first began in 1982 as a simple “stick test,” which consists of a sensor probe being placed in the tailpipe exhaust stream to measure emissions. That was then replaced in 1996 with what is still the current program called Clean Air Car Check, IDEM said. That change was made to address the new testing requirements of the 1990 amendments to the Clean Air Act.

A Clean Air Car Check inspection facility in Northwest Indiana. It is one of seven in Lake and Porter counties where cars can go to get their vehicles emissions tested every two years.
A Clean Air Car Check inspection facility in Northwest Indiana. It is one of seven in Lake and Porter counties where cars can go to get their vehicles emissions tested every two years.

In Indiana, the emissions program requirement applies to gasoline vehicles that are registered in either Lake or Porter Counties. Those cars must be inspected every two years, but there is no cost to get the test.

When it comes time for an inspection, vehicle owners must take their car to one of the approved locations. All checks start with a basic visual inspection and gas cap pressure test. Then the inspector will check the emissions, though the testing method differs a bit depending on the age of the car.

Depending on the results, the driver may need to take some follow-up steps. Of vehicles inspected in the past two-year testing cycle, about 15% have failed. For those cars that do not pass, they usually need some upgrades to be brought into compliance. IDEM said the most common repairs that are usually needed are to replace catalytic convertors, oxygen sensors and the exhaust gas recirculation valves.

Long Answer: But it’s not everywhere, and here's why

While Indiana does in fact have a program, it raises a second question: Why doesn’t the car emissions check requirement exist across the entire state?

The program was first required in Lake and Porter counties because they didn’t meet the standards under the Clean Air Act. The federal government identifies those cities that have high air pollution levels and where vehicle emissions can be a big source of unsafe contaminants such as ozone, carbon monoxide, nitrogen oxide, etc. These pollutants can affect lung and heart health, cause cancer, increase asthma rates and pollute our natural resources.

For other areas in Indiana where vehicle emissions testing is not required, IDEM said that’s because it is already meeting the federal health-based standard for ozone or is close to doing so without further action being required.

The flag flying at MacArthur Elementary School indicates the air quality.
The flag flying at MacArthur Elementary School indicates the air quality.

Ground level ozone is measured across the state, IDEM said, but only major urban areas tend to experience concentrations above the health-based standard. The Greater Chicago region is one of those major urban areas that has traditionally measured above the standard and thus requires action to mitigate the pollution.

The air quality in Northwest Indiana has “improved substantially over time,” IDEM said, and the car inspection program is one tool to make that happen.

When the Clean Air Car Check program was first implemented, the failure rate for all cars tested was nearly 40%. Then within the first four years, that rate was brought down to 25% and now, nearly 20 years later, the failure rate is around 15%.

Over time vehicles have made the necessary fixes and are better maintained, IDEM said, and as a result the failure rate has gone down.

Still, despite this success, the Lake County Council is currently suing Gov. Eric Holcomb and Attorney General Todd Rokita to eliminate the emissions testing in the county. They say it’s unfair that only Northwest Indiana counties require the emissions checks. The complaint argues that other Indiana counties have worse air quality but do not require testing.

IDEM explained, not in response to this complaint, that areas can exceed the ozone standard and still not be subject to the requirement. It depends on the severity of the ozone concentrations at the time the designations were made. Lake and Porter Counties were classified as severe — the classifications are marginal, moderate, serious, severe and extreme — at the time the program was instituted. They currently are classified as serious.

Vehicle emissions testing is mandated for areas that are classified as moderate or higher, IDEM said. Any consideration of a statewide program or one outside the federally-designated areas would require legislative action, the agency added.

There are 35 states and territories across the country that require an emissions test for cars and trucks, though the frequency and type of test varies by the state. Some states require all vehicles to be tested while others, like Indiana, have testing in only certain inspection areas.

In a few states — such as California, Illinois and Colorado — vehicle owners could have their registration renewal suspended or their registration fees doubled if they don’t have a certificate proving their car passed an emissions test.

If you have more questions about emissions or air quality, let us know! You can ask us by submitting a question through our Google form below.

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Call IndyStar reporter Sarah Bowman at 317-444-6129 or email at Follow her on Twitter and Facebook: @IndyStarSarah. Connect with IndyStar’s environmental reporters: Join The Scrub on Facebook.

IndyStar's environmental reporting project is made possible through the generous support of the nonprofit Nina Mason Pulliam Charitable Trust.

This article originally appeared on Indianapolis Star: Do you have to get you car tested for emissions? What you need to know