The test is a biennial inconvenience for hundreds of thousands of people to catch a few cars that need to be fixed.
A state audit found that 93 percent of cars pass and recommended changes to allow fewer drivers to have to take the test.
"It is an inconvenience I agree, but it's only once every other year for most folks. [It's] just like going to the dentist, though it may be inconvenient, there's a real benefit that you see from it," Will Allison, who oversees emissions testing for the state, said. "Cars are the number one source of air pollutants that form ground-level ozone."
High levels of ground-level ozone can lead to respiratory problems. Denver has more than the federal government says is safe.
The testing program takes 9,200 tons of emissions out of the air each year.
"We're trying to determine is it really still cost effective and are we having the impact on the ozone that the EPA requires us to have?" Colorado State Representative Angela Williams said. Williams is the incoming chair of the legislature's audit committee.
The regular state audit found that each ton of emissions the testing eliminated cost $7,200. That cost includes the fees and the inconvenience of taking the test.
As more modern cars replace older ones on the road, the number that fail is shrinking. A sign that the emissions problem is fixing itself.
"It could be the beginning of an end and we'll have to evaluate that as an audit committee," Williams said.
Allison thinks the emission program is still cost effective. He adds that roadside vans have been deployed to make testing more convenient and that the cost to drivers hasn't gone up in 15 years.
Still, his office is recommending changes to make it better.
Instead of having to test new cars when they're four years old, they want to test cars after they've been on the road seven years. That would save people tens of millions of dollars.
Lawmakers seem to have an appetite for that change but say they want to see it made quickly.
The audit recommended letting cars get even older. It suggested not testing cars newer than 2001, a move that would save $30 million annually.
The state board that oversees the program will consider the change to a 7-year exemption on December 20.
(KUSA-TV © 2012 Multimedia Holdings Corporation)