So far, the effort has resulted in filing cases against a dozen diesel aftermarket defeat device sellers or fleets tampering with trucks, not including cases filed against other transportation modes, Belser said.

In a December agency “alert,” EPA reminded vehicle owners that the Clean Air Act prohibits anyone from manufacturing, offering for sale, selling, or installing any part or component that bypasses or defeats emissions controls.

“Our recent enforcement alert highlights the agency has resolved civil and criminal enforcement cases involving tampering and aftermarket defeat devices for medium-duty and heavy-duty trucks,” the agency said on Feb. 17. “

One manufacturer was slapped with a $1.1 million fine for selling more than 5,500 truck aftermarket products; A hauling service for the oil and gas industry paid a $2 million penalty and one of its employees was sentenced to six months to prison.

The American Trucking Associations warned the industry last month about the national priority effort, and the possible repercussions of installing or buying the aftermarket emissions defeat devices.

“My advice is be aware that this is happening and do an assessment of your operations in your vehicles to make sure that you’re not caught up in the web,” Glen Kedzie, ATA’s energy and environmental affairs counsel, told TT.

The devices are not only illegal, they also are unfair to truckers who abide by regulatory emissions requirements, said Belser.

“When they tamper they’re putting people’s health at risk, and undercutting those people that take the time and expense to do it right,” he said. “Our goal is not to catch people, it’s to prevent violations.”