Companies located in nonattainment areas may apply for permits to increase emissions, but they must be balanced by equal or greater decreases in emissions in the same nonattainment area, called an “offset.” These offsets require companies to either reduce emissions from another part of their company or find another company with decreasing emissions to balance out their increase in emissions. The goal is to allow for continued economic development, while still working towards the goal of improved air quality.
Offsetting works to improve air quality because ozone is a regional pollutant. Reductions of VOCs or NOx even miles away can end up reducing ozone pollution in the nonattainment area since ozone can be transported from other locations.