Frequently asked questions about the EPA’s Tier 4 emission regulations.

What is Tier 4?

The U.S. Environmental Protection Agency (EPA) initiated the first emission standards for off-road engines more than 13 years ago. With each new stage or tier, EPA standards have established lower allowable emissions. EPA regulations are generally consistent with European, Japanese and Canadian rules, demonstrating a cooperative international approach to addressing this issue.

Tier 4 emission standards introduce substantial reductions of the main pollutants in emissions: carbon monoxide, hydrocarbons, nitrogen oxides (NOx) and particulate matter (PM). Emission limits are particularly focused on curbing airborne NOx and PM. These standards represent the biggest step toward reaching near-zero emissions from heavy equipment.



Why is the EPA making these changes?

According to the EPA, off-road engines are responsible for 47 percent of PM and 25 percent of nitrogen monoxide and NOx emissions from all mobile sources nationwide.

NOx is produced during combustion when the engine is at its hottest. PM—tiny carbon particles and other poisonous substances—is created when all the fuel is not burned during combustion, usually when the engine is cooler. When inhaled repeatedly, these small particles may aggravate asthma and allergies or cause other serious health problems.

Will I still be able to buy older equipment from my dealership?

Tier 4 emission requirements apply to new equipment. The requirements are not applied retroactively to existing equipment.


What will this mean for older equipment trade-ins?

The emissions performance of existing equipment should be evaluated when considering a trade-in or resale opportunity. Equipment owners looking to acquire or sell older equipment should be aware that some states are considering enacting more stringent emission regulations than the EPA requirements. Some municipalities and state DOTs are requiring that these stricter guidelines be met to participate in the bidding process for government purchases and contracts.

How are the new engines different from the old ones?

Most manufacturers are selecting one of two technologies to meet Tier 4 Interim requirements: selective catalytic reduction (SCR) and cooled exhaust gas recirculation (CEGR). 

In an SCR system, the engine is tuned for maximum efficiency. The higher combustion temperatures reduce PM levels but increase NOx levels. SCR is an after-treatment-only system that creates a chemical reaction by adding diesel exhaust fluid (DEF). This transforms the NOx into nitrogen and water, which occur naturally in the atmosphere. 


No particulate filter is required because PM levels are low due to the higher combustion temperatures.

SCR allows for a cool-running, quiet system that is separate from the main engine function and does not compromise horsepower or torque. It does not interfere with engine performance and actually improves performance because it allows the engine to breathe more freely. The after-treatment system is composed of a supply module, a DEF tank, a dosing module and an SCR catalyst.

The second technology option for meeting Tier 4 Interim requirements is the cooled-EGR approach. In a cooled-EGR system, exhaust gases are cooled, blended with fresh air and then returned to the cylinder, lowering combustion temperatures and dramatically reducing NOx.

The cooler combustion temperature results in a higher PM level, which is then reduced through the use of an after-treatment diesel particulate filter (DPF) system. The DPF requires periodic regeneration for optimal operation. This re-gen process is usually automatic, without requiring operator intervention.

At Case, we see advantages to both technologies, depending on engine size and load and application demands. Many manufacturers are applying the technology that achieves the lowest operating costs, depending on each model’s engineering characteristics and application requirements. Some solutions integrate each model’s engine, hydraulic and electronic systems to achieve the most efficient and powerful performance.


Case SCR engine technology applies a very efficient combustion process which will consume less fuel.

How will the new standards be monitored? Will it change the way I manage my equipment?

Maintenance for both systems is easy. The SCR system only requires regularly filling the DEF tank. Each machine will include a DEF gauge, and a warning signal will alert the operator when the DEF level is running low. Refilling the DEF tank can be done as part of the regular maintenance when checking fluid levels or when refueling. The DEF tank capacity is built for each model to ensure every fill of DEF lasts at least as long as two fills of diesel for mid-sized machines, such as wheel loaders, and four fills for big equipment, such as excavators.

Some manufacturers offer a cooled-EGR solution that does not change the basic engine technology dramatically from Tier 3, requiring only slight adjustments to normal service and maintenance processes.

What are the long-term benefits of the Tier 4 regulations?

The overall goal of the Tier 4 regulations is a 90-percent reduction in NOx and PM from Tier 3 standards. The reduction in PM and NOx mandated by Tier 4 standards will provide important public health benefits. The EPA estimates that by 2030, controlling these emissions has the potential to annually prevent 12,000 premature deaths, 8,900 hospitalizations and 1 million lost work days. The benefits of clean air and clean jobsites will gain the appreciation of contractors and equipment operators as the use of Tier 4-certified equipment becomes widespread. Tier 4 also provides an excellent example of industry sustainability to the general public and business community as a whole.

Effective Dates for Tier 4 Regulations

Jan. 1, 2011  Engines greater than 174 horsepower (130 kilowatts) must meet Tier 4 Interim requirements.

Jan. 1, 2012 Tier 4 Interim requirements take effect for engines in the 75 to 174 horsepower (57 to 130 kilowatts) range.

Jan. 1, 2014 Tier 4 final requirements take effect.


Construction Business Owner, March 2011