ASTM D6413 / D6413M−22

Vertical flame resistance test method used to assess how fabrics respond to a controlled ignition source

Understanding ASTM D6413 and The Importance of Vertical Flame Testing

ASTM D6413 is one of the most widely recognised laboratory methods for evaluating how a fabric behaves when exposed to a vertical flame. Although it doesn’t replicate the full intensity or duration of an EV fire, it does measure three critical indicators of fire performance — how long the material continues to burn, how long it glows, and the extent of structural damage left behind. These measurements provide a reliable benchmark for understanding how protective fabrics manage ignition, heat exposure, and flame persistence.

For EV fire blankets, this test is particularly relevant. Lithium-ion incidents evolve rapidly and produce extreme heat, so any containment blanket must resist ignition, minimise flame spread, and retain its integrity long enough for responders to take control of the scene. Strong ASTM D6413 performance is therefore a key marker of material quality, durability, and operational reliability in demanding fire-response environments.

How Fire Cloak™ Meets ASTM D6413

Although the ASTM D6413 test does not replicate the full severity of an EV fire, it provides a clear, comparable measure of how a textile responds to direct flame exposure. Independent laboratory testing has confirmed that the specialist fabrics used in Fire Cloak™ EV blankets perform exceptionally well across all three indicators assessed by this method: they resist sustained burning, minimise afterglow, and maintain structural integrity with only limited charred area.

These results demonstrate that the Fire Cloak™ material is purpose-built for high-heat environments. In real-world lithium-ion incidents—where rapid escalation, radiant heat, and unpredictable flame behaviour are common—strong vertical flame resistance is a crucial foundation for effective containment.

ASTM Test Reports

ASTM D6413 Test ReportASTM D6413 Test Report
Specimen NumberAfter Flame (seconds)After Glow (seconds)Char Length (inches)
LengthWidthLengthWidthLengthWidth
10.00.03.20.00.40.2
20.00.00.00.00.20.2
30.00.09.30.00.60.3
40.00.00.00.00.20.2
50.00.00.00.00.30.3
Avg0.00.02.50.00.30.2

ASTM D6413 Test ReportASTM D6413 Test Report
ASTM D3776/D3776M-20
Standard Test Method for Mass per Unit Area Fabric Weight-Option C Small Swatch
Preconditioning:None
Conditioning:In accordance with ASTM D1776
Selvages Included:No
Fabric Mass (oz/yd2):15.4
Fabric Mass (g/m2):521
ASTM D6413/D6413M-22
Standard Test Method for Flame Resistance of Textiles (Vertical Test)
Modifications:Afterglow time is not recorded.
Preconditioning:None
Length Direction
12345AVG Length
Afterflame Time (sec)0.00.00.00.00.00.0
Char Length (mm)0.00.00.00.00.00.0
Melting?NNNNNNone
Dripping?NNNNNNone
Melting and Dripping?NNNNNNone
Width Direction
Afterflame Time (sec)0.00.00.00.00.00.0
Char Length (mm)0.00.00.00.00.00.0
Melting?NNNNNNone
Dripping?NNNNNNone
Melting and Dripping?NNNNNNone

ASTM D6413 Test ReportASTM D6413 Test Report
Specimen NumberAfter Flame (seconds)After Glow (seconds)Char Length (inches)
LengthWidthLengthWidthLengthWidth
10.00.00.00.01.41.2
20.00.00.00.01.21.3
30.00.00.00.01.41.5
40.00.00.00.01.31.1
50.00.00.00.01.51.3
Avg0.00.00.00.01.41.3

What This Means in Practice

The ASTM D6413 vertical flame test doesn’t replicate the full intensity of a lithium-ion fire, but it does provide a reliable indicator of how a fabric behaves when directly exposed to a controlled ignition source.

Strong performance in this test demonstrates that a material can resist sustained burning, limit glow once the flame is removed, and maintain its structural integrity after exposure — all of which are essential characteristics for any fire-containment blanket used around electric vehicles.

Below is what these results mean for different decision-makers and operational teams.

A material that performs well in ASTM D6413 testing gives you a clear, independent benchmark for flame resistance — something procurement teams can confidently document and justify. It provides tangible evidence that the product uses a high-grade technical fabric designed to limit flame spread and withstand heat exposure. This supports internal compliance checks, supplier assurance processes, and due-diligence requirements when selecting safety-critical equipment.

For technical teams, the results are an indication of the blanket’s underlying thermal stability and resistance to direct ignition. Low flame persistence and controlled char development suggest that the material is engineered to maintain strength during short-duration flame exposure — a critical factor when evaluating the performance of containment equipment for EV bays, workshops, test facilities, and high-risk environments. It also helps inform risk assessments and operational readiness plans.

Frontline crews rely on equipment that will not fail under heat pressure. A blanket that exhibits minimal afterflame and limited glow ensures there is no unexpected flame propagation when managing an incident. Demonstrating strong ASTM D6413 performance helps confirm that the material will retain its integrity during deployment, giving responders more time and stability when containing lithium-ion battery fires or preventing escalation.

Whether managing a depot, car park, delivery hub, or charging area, having equipment tested for vertical flame resistance supports safer everyday operations. It provides reassurance that the containment blanket is built from materials that will not readily ignite or deteriorate if exposed to a localised flame source — a vital consideration for environments where multiple vehicles, charging stations, or personnel are present.

From a risk-modelling perspective, ASTM D6413 results supply measurable, independent evidence of material behaviour. Strong vertical flame performance contributes positively to mitigation strategies and helps demonstrate that the organisation is taking responsible steps to manage the unique fire risks associated with lithium-ion technology. This can support insurance conversations, compliance reporting, and liability documentation.

Certified Proof & Next Steps

Fire Cloak™ certification is based on formal ASTM D6413 test reports issued by two independent laboratories: Diversified Testing Laboratories, Inc. and ArcWear (Kinectrics Inc.) in the United States. Each blanket size was tested individually, with the laboratories assessing afterflame, afterglow and char development in line with the standard’s procedures.

These evaluations confirm that the specialist fabrics used in Fire Cloak™ EV Blankets do not sustain burning, do not drip or melt, and exhibit very limited char formation when exposed to a controlled flame source. While ASTM D6413 does not replicate the full severity of a lithium-ion battery fire, it provides clear, measurable evidence of how the material behaves under ignition — and the results consistently demonstrate strong flame resistance and structural stability.

Together with field use, operational trials and industry partnerships, these certified reports give organisations reliable, independently verified assurance of material performance.

Fire Cloak™ Lithium Battery Fire Limitation Blanket (4 x 3m)

Fire Cloak™ EV Fire Limitation Blanket (8 x 6m)

Fire Cloak™ XL – EV Fire Limitation Blanket (12 x 9m)

About ASTM D6413

ASTM D6413 is one of the most widely recognised laboratory methods for assessing how textile materials react when exposed to a vertical flame. Although originally developed for apparel and industrial fabrics, it is commonly used across safety-critical sectors to understand flame persistence, glow behaviour and the extent of material damage following ignition.

For Fire Cloak™, the test provides a reliable point of comparison that helps demonstrate the underlying fire-resistant qualities of the fabric used in its construction.

ASTM D6413 focuses on evaluating a material’s reaction to direct flame exposure in a controlled, repeatable environment. Its purpose is to measure whether a fabric continues to burn once the flame is removed, whether it continues to glow, and how far heat damage propagates through the material.

These indicators provide insight into the fabric’s inherent fire-resistant properties, helping manufacturers, engineers and safety professionals compare different materials using a common benchmark. While the test does not recreate the extreme heat, duration or thermal load of a lithium-ion battery fire, it offers a clear view of how a textile behaves at the point of ignition — an important factor when selecting fabrics for fire-containment applications.

ASTM D6413 focuses on three measurable outcomes that describe how a fabric behaves when exposed to a vertical ignition source. Together, these indicators provide a clear picture of the material’s response to flame, heat, and subsequent thermal effects.

Afterflame time
How long the material continues to burn once the ignition source has been removed. Short or zero afterflame times indicate that the fabric does not sustain burning and is less likely to contribute to flame spread.

Afterglow time
How long the material continues to glow after flaming has stopped. This helps assess any smouldering behaviour that may continue within the fibres, which can be a factor in slow-developing heat damage.

Char length
The extent of visible damage following exposure. A shorter char length demonstrates that heat-affected areas remain contained, and that the material maintains structural stability after ignition.

For EV fire blankets, these three indicators provide valuable insight into how the core textile components respond to initial ignition and how well they resist degradation when exposed to sudden, localised heat.

The ASTM D6413 method uses a controlled laboratory arrangement designed to assess a fabric’s behaviour under a small, consistent flame. A sample of material is positioned vertically in a draft-free enclosure, and a calibrated burner is placed beneath the lower edge of the specimen. This ensures the flame meets the fabric in the same way every time, allowing for reliable comparison between different materials and fabric constructions.

Only the conditions necessary to create a consistent ignition source are controlled — such as flame height, gas type and exposure duration. No external forces, air movement or additional heat sources are introduced. By keeping the setup simple and repeatable, the test isolates the fabric’s natural response to ignition without interference from other variables.

For products like EV fire blankets, this setup provides a useful baseline for understanding how the textile performs when exposed directly to a flame, even though real-world lithium-ion incidents involve far greater temperatures and more complex conditions.

During the test, the fabric is exposed to a small, controlled flame for a short, predefined period. The aim is not to replicate real fire scenarios, but to observe how the material behaves at the moment of ignition and immediately afterwards. Once the exposure time has elapsed, the flame is removed and the fabric’s reaction is closely monitored.

Observers record whether the material continues to burn, whether it glows after flaming stops, and how far heat-related damage extends through the sample. No mechanical forces or external stimuli are added; the assessment focuses entirely on the material’s inherent properties.

This approach provides a simple yet effective way to compare fabrics using consistent criteria.

For Fire Cloak™, the method offers valuable insight into how the blanket’s specialist textile reacts when flame first makes contact — a critical consideration for safety equipment designed to operate in unpredictable, high-heat EV environments.

The outcomes of ASTM D6413 testing are based on direct observation and measurement immediately after the flame exposure. Each indicator — afterflame time, afterglow time, and char length — is assessed separately, giving a rounded view of how the material responds during and after ignition.

Afterflame and afterglow are timed using straightforward stop-watch measurements. The shorter these durations, the less the fabric contributes to ongoing combustion once the ignition source has been removed.

Char length is determined by measuring the extent of visible heat damage on the specimen after it has cooled. A contained, minimal char area suggests the material has resisted flame penetration and retained its structure.

These results are not converted into a pass/fail rating by the test itself; instead, they provide objective data that manufacturers and safety professionals can interpret according to their own operational requirements. For Fire Cloak™, consistently low afterflame and char values demonstrate the underlying fire-resistant quality of the blanket’s textile layers and reinforce its suitability for high-risk environments.

ASTM D6413 provides a useful benchmark for understanding how a textile behaves when it first encounters a flame. It reveals whether the material will sustain burning, whether it continues to glow, and how far heat damage spreads immediately after exposure. These are important indicators of fire resistance and help compare different fabrics using consistent criteria.

However, the test is not designed to replicate the conditions of a lithium battery fire. EV incidents involve extreme temperatures, thermal runaway, rapid energy release and prolonged exposure — all far beyond the scope of a small, controlled laboratory flame. The test therefore offers insight into ignition behaviour, not full-scale fire performance.

For organisations assessing fire-containment equipment, the value of ASTM D6413 lies in what it does show: the fabric’s inherent resistance to burning, its ability to limit flame spread, and its capacity to retain structural integrity after a localised ignition event. These qualities form a strong foundation for products like Fire Cloak™, which must perform reliably in fast-moving, high-heat environments.

The full ASTM D6413/D6413M document is available exclusively through ASTM International.

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