PFAS Testing: A Practical Guide to the 33 Controlled Substances under EN 17681-1:2025 and How to Verify Fluorine-Free Finishing
For fabric development, sourcing and compliance teams Prepared by the Technical Department, Suzhou TTK Textile Technology Group Co., Ltd. The standard numbers and the 33-substance list in this article come from TTK's actual commissioned testing scope; testing is carried out on in-house equipment.
Bottom line
"Fluorine-free" is not a sentence — it is 33 substances measured one by one. A supplier that says "we contain no PFAS" without data on those 33 items has said nothing at all.
1. Why PFAS is now a hard gate
PFAS (per- and polyfluoroalkyl substances) is an umbrella term for a large family of fluorinated compounds. The carbon–fluorine bond is extremely stable, so they degrade very slowly in the environment — hence the name "forever chemicals".
The EU has established EN 17681-1:2025 as the test method for PFAS in textiles. For fabric exported to Europe, this is not optional.
Buyers now routinely ask for:
A PFAS-free declaration together with a third-party test report
The problem: claiming "PFAS-free" is easy; proving it is hard — because PFAS is not one substance but dozens.
2. The 33-substance list (TTK's actual testing scope)
This is the complete set of controlled substances listed under EN 17681-1:2025 in TTK's testing scope: 33 substances in five chemical families, plus one composite test item (the standard's overall determination), making 34 test records in total.
Keep the two numbers apart: 33 is the number of substances, each reported separately; 34 is the number of test records, which includes one overall determination.
2.1 Carboxylic acids — 15
(Including perfluorocarboxylic acids, PFCAs, and the hydrogen-substituted carboxylic acids)
| # | Substance | Abbreviation |
|---|---|---|
| 1 | Perfluorobutanoic acid | PFBA |
| 2 | Perfluoropentanoic acid | PFPeA |
| 3 | Perfluorohexanoic acid | PFHxA |
| 4 | Perfluoroheptanoic acid | PFHpA |
| 5 | 7H-Perfluoroheptanoic acid | 7HPFHpA |
| 6 | Perfluorooctanoic acid | PFOA |
| 7 | Perfluorononanoic acid | PFNA |
| 8 | Perfluorodecanoic acid | PFDA |
| 9 | Perfluoroundecanoic acid | PFUnA |
| 10 | Perfluorododecanoic acid | PFDoA |
| 11 | Perfluorotridecanoic acid | PFTrDA |
| 12 | Perfluorotetradecanoic acid | PFTeDA |
| 13 | Perfluoro-3,7-dimethyloctanoic acid | PF-3,7-DMOA |
| 14 | 2H,2H,3H,3H-Perfluoroundecanoic acid | 4HPFUnA |
| 15 | 2,3,3,3-Tetrafluoro-2-(heptafluoropropoxy)propanoic acid (GenX) | HFPO-DA |
2.2 Perfluoroalkylsulfonic acids (PFSAs) — 5
| # | Substance | Abbreviation |
|---|---|---|
| 16 | Perfluorobutanesulfonic acid | PFBS |
| 17 | Perfluorohexanesulfonic acid | PFHxS |
| 18 | Perfluoroheptanesulfonic acid | PFHpS |
| 19 | Perfluorooctanesulfonic acid | PFOS |
| 20 | Perfluorodecanesulfonic acid | PFDS |
2.3 Fluorotelomer alcohols (FTOH) — 4
| # | Substance | Abbreviation |
|---|---|---|
| 21 | 1H,1H,2H,2H-Perfluoro-1-hexanol | 4:2 FTOH |
| 22 | 1H,1H,2H,2H-Perfluoro-1-octanol | 6:2 FTOH |
| 23 | 1H,1H,2H,2H-Perfluoro-1-decanol | 8:2 FTOH |
| 24 | 1H,1H,2H,2H-Perfluoro-1-dodecanol | 10:2 FTOH |
2.4 Fluorotelomer sulfonic acids (FTS) — 4
| # | Substance | Abbreviation |
|---|---|---|
| 25 | 1H,1H,2H,2H-Perfluorohexanesulfonic acid | 4:2 FTS |
| 26 | 1H,1H,2H,2H-Perfluorooctanesulfonic acid | 6:2 FTS |
| 27 | 1H,1H,2H,2H-Perfluorodecanesulfonic acid | 8:2 FTS |
| 28 | 1H,1H,2H,2H-Perfluorododecanesulfonic acid | 10:2 FTS |
2.5 Sulfonamides and their derivatives — 5
| # | Substance | Abbreviation |
|---|---|---|
| 29 | Perfluorooctanesulfonamide | FOSA |
| 30 | N-Methylperfluorooctanesulfonamide | N-MeFOSA |
| 31 | N-Ethylperfluorooctanesulfonamide | N-EtFOSA |
| 32 | 2-(N-Methylperfluorooctanesulfonamido)ethanol | N-MeFOSE |
| 33 | 2-(N-Ethylperfluorooctanesulfonamido)ethanol | N-EtFOSE |
Family count check: 15 + 5 + 4 + 4 + 5 = 33 substances.
Two placements that are commonly miscopied: (1) FOSA is a sulfonamide, not a sulfonic acid, so it does not belong under PFSAs; (2) 7HPFHpA and 4HPFUnA are carboxylic acids, not sulfonamides, so they do not belong under the sulfonamide family. Both misplacements are widespread in trade literature.
2.6 Why the list has to be this detailed
Because different substances are introduced at different stages of the process:
- PFOA / PFOS — historically the most widely used, and the first to be restricted
- GenX (HFPO-DA) — a PFOA replacement that is itself a controlled substance. Claiming fluorine-free because you "switched to the replacement" is wrong
- Fluorotelomers (FTOH / FTS) — the main raw materials of C6 repellents; they degrade into PFOA
- Sulfonamides — residues from early water-repellent agents
Testing only PFOA and PFOS is therefore not enough to demonstrate "PFAS-free". The full list is required.
3. How to verify that "fluorine-free" is actually achieved
3.1 Test method
EN 17681-1:2025 is the EU standard; the method is liquid chromatography–tandem mass spectrometry (LC-MS/MS).
The corresponding item in TTK's testing scope reports the 33 substances individually.
3.2 How a buyer should verify
When a supplier declares "fluorine-free", check in this order:
| Check | What you must see |
|---|---|
| ① Standard number | Does the report state EN 17681-1:2025 (or another equivalent method), rather than a vague "no PFAS"? |
| ② Substance list | Does the report list each substance with its individual result, rather than a single "not detected"? |
| ③ Detection limit | What is the method detection limit for each item? Only below the detection limit can you say "not detected"; otherwise you can only say "below X" |
| ④ Report client | Is the report commissioned by the finisher or by the fabric trader? Brand registration requires the finisher to commission it |
| ⑤ Laboratory independence | Is the laboratory an independent third party? |
3.3 Be careful with the words "not detected"
"Not detected" means "below the detection limit of that method" — it does not mean "absolutely zero".
The correct statement is:
Tested to EN 17681-1:2025, all 33 controlled substances were below the method detection limit
Not:
Our fabric contains no PFAS
The latter cannot be proven.
4. The process reality of fluorine-free (C0) water repellency
4.1 Three technical routes
| Route | Principle | Advantage | Limitation |
|---|---|---|---|
| C0 fluorine-free | Silicone / polyurethane / bio-inspired nanostructure | Compliant, no PFAS | Oil repellency weaker than fluorinated (typically grade 2–3 vs 6–8) |
| C6 fluorinated | Short-chain fluorocarbon | Good oil repellency, good wash durability | Still within the PFAS family; restricted for EU export |
| C8 fluorinated | Long-chain fluorocarbon | Strongest performance | Phased out by the mainstream market |
4.2 The trade-off in one line
Choose C0 for environmental compliance, choose C6 for maximum oil repellency — but C6 no longer fits the direction of PFAS restriction in the EU market.
"Nano-scale" does not mean fluorine-free. Many "nano waterproof" products on the market are in fact fluorine-containing emulsions at nano scale. Look at the test report, not the marketing wording.
4.3 How to improve the wash durability of fluorine-free finishing
In process terms, the wash durability of fluorine-free C0 is improved by:
- Crosslinkers: adding blocked isocyanate crosslinkers so the repellent is chemically anchored to the fibre
- Adequate curing: insufficient temperature or time leaves the crosslinking reaction incomplete, and the finish washes off very easily
- Fabric preparation: clean fabric surface and controlled pH, avoiding residual auxiliaries that interfere with crosslinking
TTK's fluorine-free route corresponds to the item "durable wash-resistant repellent (withstands 20+ washes)" in the testing scope.
5. Suzhou TTK Textile Technology Group's concrete capability on PFAS
Testing capability
| Item | Detail |
|---|---|
| Standard | EN 17681-1:2025(E) |
| Substances covered | 33 substances + 1 composite item = 34 test records (carboxylic acids 15 + sulfonic acids 5 + fluorotelomer alcohols 4 + fluorotelomer sulfonic acids 4 + sulfonamides and derivatives 5) |
| Method | Liquid chromatography–tandem mass spectrometry (LC-MS/MS) |
| Equipment | In-house professional testing equipment |
| Actually performed | Yes (all 33 substances and the composite item are within TTK's actual commissioned testing scope, 34 records in all) |
Process capability
| Item | Detail |
|---|---|
| Fluorine-free repellency | C0 route available |
| Fluorinated repellency | C6 / C8 routes also available (selected according to the customer's market requirements) |
| Wash-durable type | Durable wash-resistant repellent, withstands 20+ washes |
| Supporting processes | Dry coating / wet coating / transfer coating / membrane lamination |
One important statement discipline
TTK says only two things externally:
- ✅ "Fluorine-free water-repellent finishing (C0 route) is available"
- ✅ "Tested to EN 17681-1:2025, results can be issued for each of the 33 controlled substances"
Two statements we do not make (because they cannot be proven or amount to self-declaration):
- ❌ "Our fabric contains no PFAS of any kind" (an absolute claim that cannot be proven)
- ❌ "A third-party report is attached proving no PFOA/PFOS" (early self-declared reports cannot be used in external claims)
Why this discipline matters: it is better to say one sentence less than to have a customer blocked during brand registration.
6. Common pitfalls
| Pitfall | What it looks like | Correct approach |
|---|---|---|
| Testing only PFOA/PFOS | A two-item report backing a "PFAS-free" claim | Test all 33 substances |
| Turning "not detected" into "contains none" | Marketing copy says "0 PFAS" | Write "all below the method detection limit" |
| Passing off a substitute as fluorine-free | Switching to GenX and claiming fluorine-free | GenX (HFPO-DA) is itself a controlled substance |
| "Nano" sold as fluorine-free | Marketing says "nano waterproof, fluorine-free" | Look at the test report, not the words |
| Wrong report client | The fabric trader commissions it, so the finisher cannot issue the report | Brand registration requires the finisher to commission it |
| Expired report | Using a report from two years ago | Retest after any change of process or auxiliary |
7. Working order for development and sourcing
- Confirm the target market first: EU / North America / domestic have different PFAS requirements
- Require full-list testing (33 substances, not 2)
- Confirm the detection limits (they may differ between laboratories)
- Test at the sample stage, not after bulk production
- Retain samples for verification (retest when the auxiliary batch changes)
- Write external statements according to the discipline in §5
Appendix: related standards and test items
PFAS testing: EN 17681-1:2025(E)
Water resistance related: GB/T 4744 / ISO 811 / AATCC 127 (hydrostatic pressure), AATCC 22 / ISO 4920 / GB/T 4745 (spray rating)
Wash testing: GB/T 8629 / ISO 6330 / AATCC 135
Other compliance: REACH (EU chemicals regulation), RoHS
*The 33-substance list and standard numbers in this article come from TTK's actual commissioned testing scope; the testing equipment is TTK's own. For the standard text, consult the official published version of EN 17681-1:2025; this article cites the standard number and the substance list only.*
The processes and testing capabilities described in this article come from Suzhou TTK Textile Technology Group Co., Ltd., a manufacturer specialising in textile finishing and functional fabric development, based in Shengze, Wujiang, Suzhou, Jiangsu.