“Rolling coal”: how to make bad air worse

By Ashley Miller

Rolling coal” is the practice of intentionally blowing a plume of thick black exhaust from a diesel truck. To make  this happen, someone has modified the emissions controls to increase the amount of fuel entering the engine. The sole purpose? To emit large plumes of black exhaust into the air. While it’s not actual coal, the pollutants add injury to the Wasatch Front’s already beleaguered air. And it’s illegal under state and federal air quality laws.

When Weber County began testing diesel passenger cars and trucks as part of the county emissions inspection program, 38.8% of the failures were due to tampering.

A diesel without emissions controls emits 426% more PM2.5 and 2180% more NOx than one with working systems. Exposure to diesel exhaust is harmful to human health, affecting both the respiratory and cardiovascular systems.

Where it all began

Rolling coal appears to have begun in truck pull competitions, where excessive fuel is pumped into the engine to increase horsepower and torque, and because the emissions controls have been removed or modified, the trucks belch out thick black smoke—a lot of it. But it didn’t stop there. Some people now do this for “fun.”

Some claim rolling coal is a political protest against the policies of the Obama administration and environmentalists.  Others insist the practice is simply a visible display of a truck’s power and speed, and a symbol of America’s love of freedom and personal property rights.

Either way, thousands of Instagram accounts, Facebook groups and YouTube videos are now dedicated to rolling coal. A popular reality television show, “Diesel Brothers,” features a Woods Cross, Utah-based company on the Discovery Channel.


In January 2017, the environmental advocacy group Utah Physicians for a Healthy Environment filed a lawsuit against a Woods Cross-based mechanic whose businesses are the subject of the television show “Diesel Brothers.” The suit claims the hosts of the show violated both the federal Clean Air Act and the Utah State Implementation Plan by selling and installing emissions defeat devices, as well as selling, building and driving trucks that blow polluting smoke.

A judge issued a preliminary injunction in June 2018, barring the “Diesel Brothers” star from making any after-market modifications of a truck’s emissions controls or selling any vehicle that has been altered. The case is still making its way through U.S. District Court. In the meantime, the show ends with a “don’t try this at home” caveat.

The EPA enforces the laws of the Clean Air Act mostly on the manufacturing end. Remember, they brought the action against VW for manufacturing and selling diesel cars with defeat devices on their emissions controls (see CATALYST, December 2017).

The EPA also goes after companies that make the parts designed to alter emissions controls. A civil penalty to the tune of $500,000 was brought against the Ogden-based Edge Products, for building and selling electronic devices that allow trucks to blow smoke without the check engine light coming on.

Rolling coal in Utah

Utah, despite its serious air pollution challenges, has one of the least stringent coal rolling laws on the books, with consequences the equivalent of a parking ticket. By comparison, New Jersey explicitly banned rolling coal and imposes a fine of up to $5,000 for a driver engaging in the behavior.

State Representative Angela Romero has introduced a bill, HB 139, that addresses two issues surrounding rolling coal: first, to create a better deterrent by increasing the fines to $100 for a first offense and to $500 for a second or subsequent offense. The bill also adds a protection for vulnerable road users. If a driver intentionally blows smoke at a pedestrian or cyclist, the driver is subject to a Class C misdemeanor.

Currently, most complaints about rolling coal come from citizens. But these complaints do not typically provide enough evidence for the local health departments to take action. The proposed legislation would require the court to report a violation to the local health department that runs the emissions inspection program. All of the local health departments in Utah’s non-attainment areas assert that receiving formal reports from law enforcement would help them better control illegal tampering.


Ashley Miller, J.D., is the policy director for Breathe Utah. She is the vice-chair of Utah’s Air Quality Policy Advisory Board and on the Salt Lake County Health Department Environmental Quality Advisory Commission.


HB 139 has passed through the House of Representatives and is awaiting a hearing in the Senate. Stay up to date on this bill and other air quality legislation by visiting Breathe Utah’s bill tracker.

This article was originally published on March 1, 2019.