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. 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.
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?
We test every production batch through accredited third-party labs (SGS, AITEX) and provide full specimen-level reports — not just summary certificates. Contact our team for current documentation on any style in our catalog.
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