“Overview: This standard establishes requirements for point-of-use (POU) and point-of-entry (POE) ultraviolet systems and includes two optional classifications. Class A systems (40,000 uwsec/cm2) are designed to disinfect and/or remove microorganisms from contaminated water, including bacteria and viruses, to a safe level. Class B systems (16,000 uw-sec/cm2) are designed for supplemental bactericidal treatment of public drinking water or other drinking water, which has been deemed acceptable by a local health agency.” (source)

• Ultraviolet light waves generated by the system kill bacteria and other micro organisms as they pass through.
• You may find these systems under sinks and often times hooked up in series with some sort of activated carbon filter and/or a sediments screen.
• Ultraviolet disinfection systems typically do an excellent job of killing parasites and bacteria.
• Class-A ultraviolet disinfection systems protect against viruses and harmful bacteria.
• Class-B ultraviolet disinfection systems protect against forms of bacteria not typically responsible for causing diseases.