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Glass & Cotton

Certifications

A certification mark is a narrow promise, and the narrowness is the point

Every mark here certifies something specific and real. Every one is also routinely cited as proof of something it never claimed.

Close-up of woven organic cotton fabric showing the fiber texture

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Start with OEKO-TEX

It is the mark shoppers most often read as an organic claim, and it is not one. Understanding that gap is most of what you need to read the others correctly.

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The reason certifications matter on a site like this is simple: they are the only claims in the lower-tox market that someone other than the seller has checked. A brand saying its coating is safe is a brand saying something about itself. A GOTS certificate number means an approved certification body audited a facility and can be asked about it.

The reason certifications mislead is equally simple. Each one has a defined scope, and a product can be legitimately certified while being silent about the thing you actually care about. OEKO-TEX STANDARD 100 tests for harmful substances and says nothing about organic fiber. GREENGUARD Gold measures what off-gasses, which means a substance that does not off-gas is invisible to it. A Proposition 65 warning is a disclosure threshold, not a safety finding — and the absence of a warning carries real information while its presence carries less than people assume.

Each page below leads with what the standard does not cover. That is deliberate. It is the single most useful and least-published fact about every mark in this market, and it is what lets you tell a meaningful certification from a logo on a product photo.

The marks that appear on products we cover

Certification scope at a glance
MarkDomainCertifiesSilent on
GOTSTextilesOrganic fiber plus processing chemistry, wastewater, social criteria, whole chainComfort, durability, finished-item certification unless stated
OEKO-TEX STANDARD 100TextilesFinished article tested against 1,000+ harmful substances by skin-contact classOrganic content, labour, environmental impact
NSF/ANSI 42, 53, 58Water treatmentSpecific contaminant reduction claims, verified by testContaminants outside the certified claim list
MADE SAFEMany categoriesFull-formula screening against substances known or suspected to harm healthPerformance, supply-chain labour
GREENGUARD GoldFurniture, mattressesChemical emissions in a chamber testComposition. A non-volatile substance does not show up
Prop 65Everything sold in CaliforniaNothing. It is a warning requirement, not a certificationWhether the product is safe or unsafe

How to verify a claim in two minutes

  1. Find a number, not a logo. GOTS, OEKO-TEX and NSF all issue identifiers tied to a specific company or product.
  2. Check what was certified. Fiber, a component, or the finished product? "Made with GOTS-certified cotton" and "GOTS-certified finished product" are different claims and the second is much stronger.
  3. Check the claim list, for water filters especially. NSF/ANSI 53 certification is always certification *for specific claims*. A filter certified for chlorine taste and odor is not certified for lead. The performance data sheet names each one.
  4. Check the date. Certifications are renewed annually. An expired certificate is not a current claim.
  5. Ask. A brand with a current certificate will send you the number. A brand that will not is giving you an answer.

The water-filter trap worth knowing about

NSF Protocol P473 was the standard that covered PFOA and PFOS reduction for point-of-use filters. On 1 June 2021 the PFOA and PFOS requirements were folded into NSF/ANSI 53 for carbon systems and NSF/ANSI 58 for reverse osmosis, and P473 was retired — products and references to it were removed.

That matters because "certified to NSF P473" still appears in marketing and in competitor articles years later. It is not a current certification. If PFAS reduction is why you are buying a filter, the claim to look for is PFOA and PFOS reduction under NSF/ANSI 53 or 58, on the performance data sheet. The water standards page covers this in detail.

Everything in Certifications

Questions people actually ask

Does OEKO-TEX certified mean organic?

No. OEKO-TEX STANDARD 100 certifies that a finished textile was tested against a list of over a thousand harmful substances, in a product class set by how much skin contact it has. Organic fiber content is a separate claim under a separate standard.

Does a Prop 65 warning mean a product is unsafe?

It means the business has not established that the exposure falls below California's safe-harbour level for a listed chemical. For carcinogens the no-significant-risk level is set at not more than one excess case per 100,000 people exposed over a 70-year lifetime, and no warning is required at or below it. The warning is a disclosure requirement, not a finding of harm.

Which certification should I trust most?

The one whose scope matches your question. For organic textiles, GOTS. For what is in the fabric touching your skin, OEKO-TEX STANDARD 100. For a specific water contaminant, NSF/ANSI 53 or 58 with that contaminant on the claim list. No mark covers everything, and one that appeared to would be the least trustworthy of them.

Sources

  1. Global Organic Textile Standard (GOTS) — the standard — Whole-supply-chain certification: fiber, chemical inputs, wastewater, social criteria
  2. OEKO-TEX — STANDARD 100 — Harmful-substance testing by product class. Not an organic-content claim
  3. NSF — Forever Chemicals and the Advancement of Filtration Standards — Why NSF P473 was retired into NSF/ANSI 53 and 58 in June 2021
  4. MADE SAFE — certification
  5. California OEHHA — Proposition 65 guidance for businesses — Safe-harbour levels, and when a warning is and is not required