Tier 4 and the History of Emissions Standards

To help you better understand how our industry will adopt Tier 4 and clean diesel technologies, Doosan encourages you to learn about the history of emissions reductions. 


As you'll see, the path to Tier 4 began more than 60 years ago. The standards for equipment reflect an ongoing emphasis to promote human health and a sustainable environment for future generations. Several key events and milestones have led to today's efforts.

Where does Tier 4 come from?
All emissions standards, including Tier 4, are a part of a federal law named the Clean Air Act. The purpose of this law is to reduce air pollution because of its hazards to human health and the environment. The Clean Air Act is managed and regulated by a national organization known as the Environmental Protection Agency (EPA).

Why did the federal government create the EPA and pass the Clean Air Act?
In the 1940s and 1950s, several world events (see below timeline) heightened awareness of the human and environmental hazards of air pollution. Over the next two decades, Congress took several steps to create emissions standards in various industries.

What are the key dates in the emissions standards story?


For five days, a cloud of air pollution overtakes the industrial town of Donora, Pennsylvania, sickening 40% of the town and killing 20 people.


London's Killer Fog - a toxic mix of fog and coal smoke - kills several thousand citizens over a four-day span. The world changes its view of air pollution.


The Air Pollution Control Act of 1955 identifies air pollution as a national problem and provides federal funding for air quality improvement.


The Clean Air Act of 1963 sets emissions standards for stationary sources (power plants, steel mills, etc.) and recognizes the dangers of motor vehicle exhaust.


The Motor Vehicle Pollution Act sets the first emissions reduction standards for automobiles.


On April 22, more than 20 million Americans gather in streets, parks and auditoriums to support a healthy, sustainable environment. Earth Day is now an annual event.


Emission standards broaden and become more stringent to automobiles and stationary sources, such as factories. Congress creates the Environmental Protection Agency (EPA) in part to assist with the implementation of these expanded standards.


As a result of emissions standards set in 1970, catalytic converters begin to appear on automobile exhaust systems.


The federal government extends timelines for emissions standards compliance, sets standards for lead amounts in gasoline, and takes steps to prevent destruction of ozone.


The EPA lowers lead standards for gasoline and limits diesel particulate emissions (PM).


Heavy-duty trucks and buses begin and complete an emissions reduction process. The end result is comparable to what Tier 4 will be for heavy equipment.


Cars and light trucks begin and complete an emissions reduciton process. The end result is comparable to what Tier 4 will be for heavy equipment.


Doosan equipment evolves to meet tiered emissions standards for diesel engines, with Tier 4 being the final step in this process.