Environmental Protection Agency (EPA) Tier 4 Interim regulations took effect in North America in January 2011 for engines above 173 hp ( 129 kW). Equivalent EU Stage IIIB regulations begin at the same time for European Union countries, while similar regulations are expected to commence in 2013 for Japan Ministry of Land, Infrastructure and Transportation (JMLIT) / Japan Ministry of the Environment (JMOE). A maximum of 15 parts-per-million (ppm) sulfur content in diesel fuel will be regulated for these off-highway applications in North America, Europe and Japan.
The EPA Tier 4 Interim and EU Stage IIIB emissions standards and effect dates vary by power category, shown below in the chart.
The regulations require a major reduction of particulate matter (PM) and also require significant oxides of nitrogen (NOx) reductions. The most stringent reductions apply across the 174-751 hp (130-560 kW) power categories with 90% PM and 45% NOx reductions. These reductions drive the need for PM exhaust aftertreatment and enhanced engine technology. The 75-173 hp (56-129 kW) power category will require over 90% PM reduction, although NOx reductions are less severe than higher-power engines.