Quick Answer
NSF/ANSI standards certify specific claims: 42 covers aesthetic effects (taste, odor, chlorine), 53 covers health effects in drinking water, 177 covers shower filtration systems for free chlorine reduction, and 401 covers emerging contaminants. A generic 'NSF' mark means little — the standard number tells you what was actually tested.
Problem
Packaging says 'NSF certified' without the standard number, so shoppers cannot tell what claim was actually verified.
Product Recommendation
ZOOSHEN will list applicable certifications per product after final validation — we do not publish certification claims before they are verified. See /technical/nsf-177.