A Buyer’s Guide to Flame Resistance Testing
ASTM D6413 / D6413M Standard Explained
The DongLian team supports OEM workwear and rainwear programs for international buyers, from specification review and sample development to bulk and private-label orders, with third-party compliance documentation for FR rainwear.
What Is ASTM D6413? A Buyer’s Guide to Flame Resistance Testing for Rainwear
If you’re sourcing flame-resistant (FR) rainwear for oil & gas, utilities, mining, or any environment with flash-fire risk, you’ve probably seen “ASTM D6413” on a spec sheet. But what does it actually measure — and how do you know if a “pass” is a strong result or barely adequate?
What ASTM D6413 Actually Tests
ASTM D6413 (also written as D6413/D6413M) is the standard test method for measuring the flame resistance of textiles using a vertical flame test — often called the ASTM D6413 vertical flame test. The SGS report discussed below was issued to the D6413/D6413M-22 edition, so always check which edition a supplier’s report cites. The fabric sample is mounted vertically, exposed to a controlled flame for 12 seconds, then the flame is removed. Testers measure what happens next.
Three numbers matter most:
- Afterflame Time How long the fabric keeps burning after the flame source is removed. Shorter is better. A true FR fabric should self-extinguish almost immediately — ideally recorded as NIL (no measurable afterflame at all).
- Afterglow Time How long the fabric continues to glow (smolder) after the flame stops. Again, NIL is the target — it means the fabric won’t keep smoldering and potentially re-igniting.
- Char Length How far the burn damage travels up the fabric, measured in millimeters. Lower char length = smaller damaged area = better protection. This tells you how much of the garment would actually be compromised in a real flash-fire event.
Reading a Real Report: Style DL1491FR Example
To make this concrete, here are the actual results from an SGS third-party test report for a PVC/polyester FR rainsuit (Style No. DL1491FR, 0.35mm coated fabric, tested per ASTM D6413/D6413M-22):
| Test Direction | Afterflame Time | Afterglow Time | Char Length (avg) |
|---|---|---|---|
| Lengthwise | NIL | NIL | 104 mm |
| Widthwise | NIL | NIL | 101 mm |
Both directions returned NIL for afterflame and afterglow — the fabric self-extinguished instantly once the flame was removed, with no lingering burn or smolder. The char length averaging ~102mm is consistent across both directions, indicating uniform coating rather than a lucky single sample. Whether a char length of about 102 mm is acceptable depends on the limit in the specification you are buying to — which is exactly why the next section matters.
ASTM D6413 Is a Test Method, Not a Pass/Fail Standard
ASTM D6413 explains how to run the vertical flame test and what to record. It does not set one universal pass line. The limits for afterflame time and char length come from the product specification, buyer requirement or tender document that calls for the test.
That is why “tested to ASTM D6413” on a spec sheet tells you very little on its own. Two reports can both cite D6413 and still be judged against different limits. Limits differ between specifications, so confirm the exact afterflame, afterglow and char length limits in the specification you are buying to.
- Which specification or buyer requirement the result was judged against
- The exact limits for afterflame time, afterglow time and char length in that specification
- Whether the reported figures — not just the word “pass” — sit inside those limits
- Whether the report covers the fabric and style you are ordering
- Whether any conditioning or laundering the specification requires was done before testing
ASTM D6413 vs ASTM F1891 vs EN ISO 14116
Buyers often see these three standards side by side. They do different jobs:
| Standard | What It Is | What to Ask the Supplier |
|---|---|---|
| ASTM D6413 / D6413M | Test method: vertical flame test for textiles (afterflame, afterglow, char length) | The full report and the limits it was judged against |
| ASTM F1891 | US specification for arc- and flame-resistant rainwear | A report that names F1891 and lists which requirements it covers |
| EN ISO 14116 | European standard for limited flame spread materials, material assemblies and clothing | The certificate and test report for the finished garment, not only the fabric |
A test report is only evidence for the standard it names. Ask which standard each document was issued against, and do not assume a result under one standard covers another. For how a European report is structured, see How to Read an EN ISO 14116 Test Report for FR Rainwear.
Why This Matters When You’re Sourcing
A supplier telling you their rainwear is “flame-resistant” is a marketing claim. A supplier handing you a dated, numbered SGS report with actual specimen-level data is giving you something you can legally verify and put in your own procurement file.
- The full test report, not just a one-page certificate summary
- The exact style number tested — it must match what you’re ordering
- A recent test date — fabric formulations and coatings change over time
- Both lengthwise and widthwise results — fabric behaves differently along each axis
Understanding the Application Limits
PVC/Polyester flame-resistant rainwear is primarily designed for limited flammability applications — such as 3-piece FR rain suits used in oil & gas field maintenance and utility work. In the market, this is sometimes referred to as disposable or limited-use FR rainwear.
Bottom Line
ASTM D6413 doesn’t tell you whether a fabric is “fireproof” — no fabric is. It tells you, in measurable terms, how a fabric behaves when exposed to flame and how much protection margin a worker has. When comparing FR rainwear suppliers, ask for the full report with specimen-level data — not just the claim.
Sourcing FR Rainwear for Your Operation?
Send us your target market and style requirements — we can share applicable third-party test documentation (SGS, AITEX) for your review, with specimen-level data where available.
Request an RFQ Explore FR RainwearFrequently Asked Questions
ASTM D6413 itself does not set a universal pass/fail limit for char length. The acceptable range depends on the product specification, buyer requirement or tender document that calls for the test. Always confirm the exact char length limit in the specification you are buying to, and compare it against the reported figures — not just the word “pass.”
No. ASTM D6413 is a vertical flame test method only — it measures afterflame time, afterglow time and char length. It does not measure arc rating (cal/cm²). For arc flash hazards, look for ASTM F1891 (arc and flame-resistant rainwear) or garments rated to NFPA 70E. PVC/polyester FR rainwear is designed for limited flammability applications, not primary arc flash or flash-fire protection.
Not automatically. A test report covers the specific fabric, style and construction that was tested. If you order a different style, color or fabric, it needs its own test report. Always confirm the exact style number on the report matches what you are ordering, and ask for both lengthwise and widthwise results.