Since 1996, U.S. environmental regulations have used a tier system to regulate emissions from ‘off-road’ diesel engines. Expect a new set of regulations covering carbon particulate matter and nitrous oxides in 2011
by RALPH WINFIELD
Up until 1994, “off-road” diesel engines, which include all farm diesel engines, were not regulated. The U.S. Environmental Protection Agency (EPA) had set lower diesel emission standards under the Clean Air Act of 1970 for “on-road” diesel engines.
The Act initially regulated emissions from automobiles and then highway trucks and buses. Over the ensuing 16 years, the emission standards became increasingly more stringent, using a “tier” or stepped system.