The requirement for meeting Tier 4 Final emission standards set by the Environmental Protection Agency (EPA) has been a phased implementation over the past decade. The final stage was fully implemented in December 2017 and now includes all off-road, diesel-engine machines ranging from 25 horsepower and above. In other words, if you are in the market to buy a new diesel-engine air compressor fresh off the factory line, it will be a Tier 4 Final model.
Previously, some manufacturers were allowed flex credits that allowed them to continue to manufacture machines at a lower tier level, such as Tier 3 and Tier 4 Interim. Now, all new equipment on the market is Tier 4 Final, regardless of manufacturer.