An approvals agency, sometimes called an authority, is a publicly recognized agency that meets certain requirements to be in the position to evaluate products, systems, components, or processes against codes, standards, laws, or regulations. 

The requirements vary depending on the jurisdiction. Some approvals agencies are brought into being by acts of parliament, such as the Canadian Standards Association.  Other agencies meet guidelines to become a nationally recognized test laboratory (NRTL).

A nationally recognized test laboratory is a private-sector laboratory that meets the requirements set out by the jurisdiction in which it operates. For example, in the USA, a NRTL must be recognized by OSHA as meeting the requirements of law 29 CFR 1910.7.  Recognition empowers an NRTL to perform testing and product certification using consensus test standards.  For a list of NRTLs see Wikipedia.

General overview of the requirements:

• Capability to test and evaluate for conformance to appropriate standards.
• Adequate controls for identification of certified products, and conducting follow-up inspection of actual production
• Complete independence from users, manufacturers, or vendors of the certified products
• Procedures for producing its findings and for handling disputes or complaints

The Occupational Health and Safety Association created by the occupational health and safety Act of 1970 in the USA and is part of the United States Department of Labor. It performs conformity assessments of NRTLs.

In Canada instead of OSHA accrediting NRTLs, it is the role of the Safety Council of Canada. The SCC is Canada’s accreditation body. The SCC accredits conformity assessment bodies, such as testing laboratories, and product certification bodies, to internationally recognized standards. 

Conformity assessment is the process of determining in practice whether a product, system, or service meets the requirements of a particular standard.