The United States Environmental Protection Agency (EPA) have guidelines, widely adopted across the world as benchmark testing criteria for microbiological filtration. Many countries have adopted these guidelines in the absence of any other international protocols and levels.
The purpose for the guidelines are established in their introduction:
"as a testing guide to manufacturers wishing to have their units considered as microbiological water purifiers, whether registered or not, and for the evaluation of such testing data; as a guide to consumers regarding what they can expect from microbiological water purifiers tested according to this standard and protocol; to assist in the research and development of microbiological treatment units for possible military applications.”
The EPA criteria and guidelines demand the following percentage reduction:
The Water-to-Go testing reports from BCS, (a major US laboratory which performs testing in accordance with NSF, EPA and NELAC protocols) shows that both sizes of filters used in the 50 cls and 75 cls bottles deliver the following results, which meet or exceed the EPA requirements: