The regulations were divided based on application last January 1, 2011. These application types are non-road mobile, stationary emergency and stationary non-emergency.
Tier 1was published in the year 1996 and it was the first set released for emission regulations. After this regulation was published, the EPA has been strict on these which resulted to engine manufacturers developing more advance innovations. After each tier of regulation is released, there has been a considerable amount of reduction in two of diesel engine’s main pollutant, nitrogen oxides and particulate matter. After a new tier is released, the EPA is giving operators two years before they can install a new engine that is able to comply with the standards.
In the case of legacy equipment, those that has complied the emission standards on the year that it was manufactured can operate in some not very strict places. The good thing about legacy equipment is they can be rebuilt and then reused just as long as the new version follows the latest emission standard in place. While those engines that were manufactured for a certain fleet cannot operate unless they meet the standard of emissions set for them.
As of date, Tier 4 emissions requirement is the strictest tier that the EPA has released for. Tier 4 is for diesel engines used in off-highway operation. Most of the power ranges are temporarily assigned under the Tier 4i which is considered an interim period while the final version of the Tier 4 is under some work. The requirements under the Tier 4i are less strict either in NOx or PM. The tier 4 requirements, for engines that are operating below 25 mechanical horsepower, came into effect last 2008. While Tier 4i is focused on engines that are operating from 25 to 48 horsepower range. In cases of engines that are operating higher than 48 horsepower, last 2011 or 2012, Tier 4i has been assigned but the requirements depend on the power range. Tier 4 emissions requirement was made final last 2013-2015 and covers engine depending on their power range. The power ranges that were used as basis are not the generator set’s electrical output but the engine’s mechanical output.