The National Environmental Laboratory Accreditation Conference (NELAC) is an organization sponsored by the United States Environmental Protection Agency (EPA) as a voluntary association of state and federal officials with private sector input. The purpose of the organization is to foster the generation of environmental laboratory data of a known and documented quality through the development of national performance standards for laboratories and other entities directly involved in the environmental field measurement and sampling process.

The objectives of NELAC include the development and improvement of standards used for qualifying a laboratory as an accredited laboratory, implementing a uniform national accreditation program, designating state and federal agencies as accrediting authorities, providing reciprocity among the NELAC accrediting authorities, and providing model language for uniform legislation and regulations. The NELAC standards also address the issues of assessor training, proficiency testing, oversight of accrediting authorities for uniform interpretation of the standards, and the use of third party assessors to carry out parts of the assessment functions.

On July 1, 1999, the New Hampshire Environmental Laboratory Accreditation Program (NH ELAP) was formally recognized as a National Environmental Laboratory Accreditation Program (NELAP) accrediting authority. NH ELAP has the authority to require that all laboratories which it accredits to be in compliance with the NELAC standards. To be accredited, a laboratory must have a quality system in place that results in the generation of data of a known and documented quality.

At this time, NH ELAP will accredit laboratories only for potable water (drinking water) and non-potable water, (wastewater and whole effluent toxicity testing) parameters. It is the intention of NH ELAP to include SW-846 / RCRA methods in its Field of Accreditation by mid 2008.