How do businesses and industry “clean” the air?

The Environmental Protection Agency (EPA) requires areas failing to attain one or more of the National Ambient Air Quality Standards (NAAQS) to prepare and execute a State Implementation Plan (SIP). The SIP is a blueprint of how the state will achieve compliance with the NAAQS by the compliance date. The Clean Air Act requires the state to revise the SIP regularly to incorporate new information as it becomes available. Only one SIP exists for each state. The original ozone SIP for the Houston region was submitted in 1973 and has been revised many times. The Texas SIP documents are available at

There have been significant improvements in air quality across Houston over the past decade. Those improvements were made by reducing ozone-forming emissions like oxides of nitrogen (NOx) and volatile organic compounds (VOCs) in every sector—industry, small business, motor vehicles and heavy-duty equipment. Many other strategies are used to reduce emissions and improve Houston’s air quality. These can range from industry installing additional emissions controls, replacing or retrofitting older vehicles and equipment with cleaner vehicles and equipment to encouraging alternative commuting, and even education and advocacy.

Houston’s air is cleaner, but challenges remain. EPA’s more stringent 2015 ozone standard means that Texans will have to reduce NOx and other emissions even more. The Texas Emissions Reduction Plan, or TERP, plays a critical role in cleaner air. TERP provides financial incentives to individuals, businesses, and local governments to reduce emissions from higher polluting vehicles and equipment. Its nine different programs are designed to help reduce emissions from different types of engines by providing grant funding for a portion of the retrofit or replacement costs. The funding comes from a portion of motor vehicle registration fees. This incentive makes it easier for individuals or businesses to justify spending money on the retrofits/replacements to get the emission reductions.

TERP is an important part of Houston’s overall clean air plan for several reasons. First, the Clean Air Act does not allow states to develop standards for motor vehicle engines and fuels. Therefore, states are extremely limited in their authority to regulate emissions from the largest two sources of NOx in Texas—on-road motor vehicles such as cars and trucks and non-road vehicles such as railroad engines and boats.

However, under the Clean Air Act, Texas is allowed to impose “use restriction” types of regulations. Such regulations can include mandating carpooling for businesses, speed limit restrictions, or forbidding landscapers and construction workers from using their equipment in the morning hours as options. In the past, these types of use restriction mandates have proven extremely unpopular with the public and some businesses. TERP will be an increasingly important source of cost-effective NOx reductions over the next decade as Texas works to meet new federal standards.

For more Information on TERP, go to