Tier 4 emission standards are the final step of a multi-year diesel emission-reduction project by the U.S. government. The first tier was introduced in 1996, and Tier 4's phase-in started in 2008 and will continue through to 2015. The purpose of these standards it to reduce pollution. They were phased in in tiers is because it is easier to gradually reduce emissions than it is to reduce them all at once.
Examine the effects of Tier 1-3 emissions standards. These standards set the foundation for Tier 4 standards, so it is important to define them in order to define Tier 4. For example, under Tier 1 diesel engines capable of 560 kilowatts could emit 11.4 grams of carbon monoxide per kilowatt. Tier 4, however, only allows 3.5 grams per kilowatt.
Look at which chemicals Tier 4 emissions covers. All of the tiers cover carbon monoxide, non-methane hydrocarbons, nitrous oxide and particulate matter.
Look at how diesel engines will have to comply with Tier 4 emissions guidelines. They will need to add advanced aftermarket add-ons, such as equipment to treat exhaust gas before it actually leaves the engine.
Examine what types of vehicles the emission standards apply to. These standards apply to non-road diesel engines, such as those in boats, factories, locomotives and other engines that do not power cars or trucks.
