ISO 15025:2016 Explained: Limited Flame Spread Testing for Protective Clothing Fabrics
ISO 15025 is an international test method used to evaluate the limited flame-spread behavior of flexible materials intended for protective clothing.
The standard includes two procedures: Procedure A applies a defined flame to the surface of a vertically oriented specimen, while Procedure B applies the flame to its bottom edge.
This guide explains how the two procedures differ, what laboratories observe, how ISO 15025 relates to protective-clothing standards and what buyers should check before purchasing flame-resistant fabric.
Video demonstration of ISO 15025 limited flame-spread testing for vertically oriented protective-clothing materials.
What Is ISO 15025:2016?
ISO 15025:2016 is titled Protective clothing — Protection against flame — Method of test for limited flame spread.
It specifies laboratory procedures for determining the limited flame-spread properties of vertically oriented flexible materials exposed to a small, defined flame.
The test can be used for single-layer fabrics and multi-component constructions, including coated, quilted, multilayered and sandwich combinations.
What Materials Can Be Tested?
ISO 15025 may be applied to flexible materials and material combinations used in protective clothing, including:
Woven flame-resistant fabrics
Knitted protective-clothing fabrics
Coated textile materials
Quilted protective materials
Multilayer fabric assemblies
Sandwich textile constructions
Seams and garment components when required by the applicable product standard
The method is not intended for situations involving restricted air supply or exposure to large sources of intense heat. It is also not appropriate for materials that demonstrate extensive melting or shrinkage.
ISO 15025 Procedure A vs Procedure B
ISO 15025 contains two ignition procedures. The correct procedure should be specified by the applicable protective-clothing standard or customer requirement.
| Comparison | Procedure A | Procedure B |
|---|---|---|
| Common Name | Surface ignition | Bottom-edge ignition |
| Flame Position | Applied to the face of the specimen | Applied to the lower edge |
| Specimen Orientation | Vertical | Vertical |
| Primary Purpose | Evaluates flame contact with the material surface | Evaluates flame contact with an exposed lower edge |
| Hole Formation | May be observed and reported | Not evaluated in the same way as surface ignition |
| Related Code | Often associated with code A1 | May be associated with optional code A2 |
Procedure A and Procedure B are not interchangeable. A test report should clearly identify which procedure was used and which material surface or layer was exposed to the flame.
Procedure A: Surface Ignition
In Procedure A, the burner flame is directed at the surface of the vertically mounted specimen. This represents a situation in which a small flame contacts the face of the protective material.
For multilayer materials, the test plan should identify which surface is exposed. Testing only the outer surface may not describe the behavior of an inner layer when it is directly exposed.
Procedure B: Bottom-Edge Ignition
In Procedure B, the defined flame is applied to the lower edge of the vertically mounted specimen.
An exposed edge can respond differently from the main fabric surface, especially in multilayer, coated or laminated materials. Procedure B may be required in addition to Procedure A by certain product standards or customer specifications.
How Is the ISO 15025 Test Performed?
Testing should be performed by a qualified laboratory using the official ISO document. The following summary explains the general sequence and is not a replacement for the standard.
1. Representative Sampling
Specimens are taken from the material in the required directions. Woven fabrics may perform differently in the warp and weft directions, so both orientations may need to be tested.
2. Required Pre-Treatment
The material may be tested as received, after washing, after cleaning or after another pre-treatment specified by the applicable product standard.
Pre-treatment is particularly important for chemically treated flame-retardant fabrics because repeated washing may change their performance.
3. Conditioning
Specimens are conditioned in the required laboratory atmosphere before testing. Moisture content can influence textile burning behavior and test repeatability.
4. Vertical Mounting
The specimen is secured vertically in the specified holder. The burner is positioned for either surface ignition or bottom-edge ignition.
5. Flame Application
A small defined burner flame is applied to the specimen for the period specified by the method. The laboratory removes the ignition source and monitors the material.
6. Observation and Reporting
The laboratory records limited-flame-spread behavior, afterflame, afterglow and other relevant observations. Pass/fail requirements normally come from the applicable protective-clothing standard rather than ISO 15025 alone.
What Results Are Recorded?
| Recorded Item | Meaning |
|---|---|
| Flame Reaching an Edge | Whether flame reaches the upper or vertical edge of the specimen |
| Afterflame Time | How long flaming continues after the ignition source is removed |
| Afterglow Time | How long glowing combustion continues after flaming ends |
| Afterglow Spread | Whether glowing combustion spreads into undamaged material |
| Debris | Whether material separates and falls from the specimen |
| Flaming Debris | Whether falling material remains flaming or ignites the indicator paper |
| Hole Formation | Whether a hole forms during surface ignition and which layer is affected |
| Damaged or Char Length | May be recorded when required by the applicable product specification |
Does ISO 15025 Provide a Pass or Fail Classification?
ISO 15025 defines a test method, but it does not create one universal classification for every protective-clothing application.
Pass/fail limits and classifications are established by related product standards. For example, ISO 14116 uses ISO 15025 Procedure A as part of its classification system for limited-flame-spread materials, assemblies and clothing.
Other protective-clothing standards may combine ISO 15025 results with requirements for heat transfer, mechanical strength, dimensional stability, seams, garment design and additional hazards.
Tested according to ISO 15025:2016, Procedure A, under the conditions identified in the laboratory report.
“ISO 15025 certified,” “completely fireproof” or “suitable for all protective clothing” without identifying the product standard and tested construction.
Standards Commonly Used with ISO 15025
| Standard | General Purpose | Relationship to ISO 15025 |
|---|---|---|
| ISO 14116 | Limited-flame-spread materials and clothing | Uses Procedure A results for classification |
| ISO 11612 | Protective clothing against heat and flame | Adds thermal-performance and garment requirements |
| ISO 11611 | Protective clothing for welding and allied processes | Uses ISO 15025 as part of broader garment requirements |
Passing ISO 15025 alone does not prove compliance with ISO 14116, ISO 11612, ISO 11611 or another complete protective-clothing standard.
What Factors Affect Test Results?
Fiber composition and blend ratio
Inherent or treated flame resistance
Fabric weight and thickness
Weave, knit and fabric density
Coating, backing and lamination
Dyes, pigments and finishing chemicals
Warp and weft directions
The exposed face of the fabric
Washing and cleaning pre-treatment
Seams, closures and garment components
A result obtained from an untreated sample may not represent performance after repeated laundering. Likewise, a report for the base fabric may not cover a finished coated or laminated construction.
What Should Buyers Check in a Test Report?
ISO 15025 edition
Procedure A or Procedure B
Related product standard and classification
Product and batch identification
Fiber composition and fabric weight
Coating, backing and multilayer construction
Tested direction and exposed face
Washing, cleaning or other pre-treatment
Afterflame and afterglow results
Flame-spread, debris and hole observations
Laboratory name, report number and issue date
Common Purchasing Mistakes
Not Specifying Procedure A or B
An order stating only “ISO 15025 required” may be incomplete. The buyer should identify the applicable ignition procedure.
Treating a Test Method as a Complete Garment Standard
ISO 15025 evaluates limited flame spread. It does not cover every requirement for garment design, heat transfer, strength, labeling or user information.
Ignoring Laundering Durability
Flame-retardant finishes may change after washing. Required pre-treatment cycles should be agreed before testing.
Using a Fabric Report for Every Garment Component
Seams, reflective tape, labels, closures and other components may require separate evaluation under the relevant garment standard.
Frequently Asked Questions
What Is the Current Version of ISO 15025?
ISO 15025:2016 remains the current published edition as of August 2026. It is undergoing systematic review, but no replacement edition has yet been published.
What Is the Difference Between Procedure A and Procedure B?
Procedure A applies the flame to the specimen surface. Procedure B applies it to the exposed bottom edge.
Is ISO 15025 the Same as ISO 14116?
No. ISO 15025 provides a limited-flame-spread test method. ISO 14116 establishes performance requirements and a classification system for limited-flame-spread materials and clothing.
Does ISO 15025 Measure Heat Protection?
It evaluates limited flame-spread behavior. It does not by itself measure all forms of convective, radiant or contact-heat protection.
Can Coated or Multilayer Fabrics Be Tested?
Yes. ISO 15025 can be applied to coated, quilted, multilayered and sandwich constructions, provided the material is suitable for this test method.
Does a Passing Result Mean the Fabric Is Fireproof?
No. The result describes the behavior of a particular specimen under defined laboratory conditions. No textile should be described as completely fireproof solely because of an ISO 15025 result.
Conclusion
ISO 15025:2016 provides two laboratory procedures for evaluating limited flame spread in vertically oriented flexible materials used for protective clothing.
Procedure A evaluates surface ignition, while Procedure B evaluates bottom-edge ignition. The report may record flame spread, afterflame, afterglow, debris and hole formation.
Buyers should specify the procedure, related protective-clothing standard, pre-treatment, fabric direction, exposed surface and complete material construction before requesting testing or placing an order.
Looking for a Flame-Resistant Protective Fabric?
Contact KIGI TEXTILE to discuss flame-resistant woven fabrics, coated textile constructions and application-specific testing requirements. Please provide the required standard, test procedure, fabric specifications, pre-treatment and final application.
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