NSF certifications for refrigerator filters, explained

Certification is specific

A certification logo is useful only when it applies to the exact model being sold and to clearly listed reduction claims. A company may sell several cartridges with different certifications, so do not assume one tested product covers an entire brand.

Look for the cartridge model in the certifier's public database and compare the listed claims with the product label. Phrases such as tested to a standard are not necessarily the same as independently certified to that standard.

Common standards

NSF/ANSI 42 generally addresses aesthetic effects such as chlorine taste and odor and certain particulates. NSF/ANSI 53 addresses specified contaminants with health effects, such as lead or cysts, when those claims are included in the certification. NSF/ANSI 401 covers certain emerging contaminants or incidental compounds when listed for the product.

• 42: aesthetic effects and specified non-health-related claims
• 53: specified contaminants associated with health effects
• 401: specified emerging or incidental compounds
• 372: lead content in drinking-water system components

What certification does not tell you

Certification does not prove that a cartridge fits your refrigerator, and a fit claim does not prove a particular contaminant reduction. Confirm both independently. Also check capacity and flow-rate conditions because certified performance is tied to the way the product was tested.

For households with a known local water contaminant, select a product certified for that specific reduction claim rather than choosing by the number of standards displayed on the package.