What is tier 4?

Wednesday, April 1, 2015
What is tier 4?

Each year, Earth Day - April 22 - marks the anniversary of the modern environmental movement. First celebrated in 1970, it was a key turning point in raising American awareness of environmental problems and within only a few months, the United States had enacted the Clean Air Act (CAA) and established the U.S. Environmental Protection Agency (EPA) to reduce pollutants expelled into the air by fossil fuel engines.

Since that time, EPA has set several standards for non-road diesel engines to decrease emissions levels of non-methane hydrocarbons (NMHC), nitrogen oxides (NOx) and particulate matter (PM). (See chart.) Signed in 2004, the next – and final – stage of emission standards, Tier 4, will push emission limits toward zero and require extensive use of new technologies and control for diesel engines by 2015.

As the final stages of Tier 4 standards are implemented; the EPA, through the CAA, mandates control of air pollution from mobile sources by regulating both the composition of fuels and emission levels of motor vehicles and non-road engines. Vehicle fuel standards require Ultra Low Sulfur Diesel Fuel (ULSD, 15PPM sulfur) and are met by the refiners. The regulation of diesel vehicle emission limits primarily targeting nitrogen oxides and particulates are met by the engine manufactures. These limits apply to on-road vehicles, off-road vehicles, and non-road sources (e.g., marine engines, locomotives, and stationary power generation).