NSF International is an organization www.nivito.com that tests and inspects water filtration products. These filters must meet the NSF specification to be certified. To get certified, manufacturers must submit product details to the NSF and have them reviewed by their staff. They will undergo evaluation, practical laboratory testing, and a manufacturing facility inspection. To maintain their certification, manufacturers must agree to reteest their products every year. This means that they must meet strict requirements for the health and safety of their customers.