An official website of the United States government.

This is not the current EPA website. To navigate to the current EPA website, please go to This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »


National Enforcement Investigations Center (NEIC): Field Science


To verify compliance with environmental laws, states or the EPA Regions deploy inspection teams to evaluate the self monitoring and assessments performed by industry. When these inspections are especially large or complex, NEIC is sometimes asked to join or lead the inspection teams. NEIC has developed a comprehensive approach to the most complex inspections called Process-Based Environmental Compliance Monitoring Investigation, which is grounded in gaining a detailed technical understanding of facility processes and the types of waste result. Regulatory applicability is then determined and the disposal practices into various media (water, air, soil, hazardous waste containers) are evaluated for compliance with applicable regulations. See Criminal Publications for details about Process-Based Environmental Compliance Monitoring Investigation.

Leak Detection and Repair Program (LDAR)

An example of an on-site monitoring program is enforcement of the LDAR regulations that affect almost all U.S. industry processes in which volatile organic compounds (VOCs) are used or manufactured which includes all oil refineries and petrochemical plants. Leaking equipment such as valves, pumps, and connectors, are the largest source of emissions of volatile organic compounds (VOCs) and volatile hazardous air pollutants (VHAPs) from petroleum refineries and chemical manufacturing facilities. Facilities can control emissions from equipment leaks by implementing an LDAR program or by modifying/replacing leaking equipment with “leakless” components. NEIC has led EPA investigations of these programs since the early 1990s, which now includes innovative, “next generation” forensic science techniques and advanced monitoring instruments such as infrared (IR) sensitive cameras which can “see” hydrocarbon emission that are not visible to the human eye.

Typical large scale petrochemical manufacturing facilities can contain over 100,000 pieces of regulated process equipment which may leak VOCs to the atmosphere. VOCs contribute to the formation of ground-level ozone, which is a major component of smog and causes or aggravates respiratory disease, particularly in children, asthmatics, and healthy adults who participate in moderate exercise. Many areas of the United States, particularly those areas where refineries and chemical facilities are located, do not meet the National Ambient Air Quality Standard(NAAQS) for ozone. Ozone can be transported in the atmosphere and contribute to nonattainment in downwind areas. Some species of VOCs are also classified as VHAPs. Some known or suspected effects of exposure to VHAPs tend to be closest to the emission source, where the highest public exposure levels are also often detected. Some common VHAPs emitted from refineries and chemical plants include acetaldehyde, benzene, formaldehyde, methylene chloride, naphthalene, toluene, and xylene. Under EPA LDAR regulations, each piece of equipment may be required to be tested for leaks several times each year. In order to fully evaluate compliance with LDAR regulations, NEIC employs relational databases to collect and evaluate this detailed facility information. Using IR cameras, NEIC can pinpoint leaks in a more efficient and cost-saving manner. NEIC’s innovation in LDAR compliance investigations has encouraged several companies to enter global settlement negotiations to resolve both LDAR and other Clean Air Act compliance issues.