Emission Inventories

All the data collected through the measurement of pollutants in the ambient air and from emissions sources is used to develop emission inventories. An emissions inventory is a quantitative list of the amounts and types of pollutants that are entering the air from all sources within a certain area. The fundamental elements in an emission inventory are the characteristics and locations of the sources, as well as the amounts and types of pollutants emitted.

An emission inventory can help identify air pollution concerns and determine the air quality goals that a certain region needs to meet. An emissions inventory is one of the most basic tools of air quality management. The emission inventory data can be used to simulate air pollution formation and transport, estimate potential pollutant concentrations in an area, and estimate the effectiveness of potential emission reduction requirements. Chemical transformation and computer dispersion models use emission data and meteorological data to project how pollutants will form and spread (disperse) across a region. In other words, emission inventories are valuable planning and evaluation tools in the air quality management system.

EPA encourages states to develop and maintain emission inventories, and provides technical assistance to help the states achieve this goal. EPA has published a number of documents to assist states and local agencies in developing inventories. Development of an inventory is a tedious and detailed task. The data that make up the inventory must be carefully collected and analyzed. Strict quality assurance guidelines must be followed to ensure the accuracy and validity of the inventory.