Camouflage Net Afterflame Time Testing: Standards, Procedures, and Requirements

Camouflage net afterflame time testing measures how long a camouflage net continues to burn with visible flame after the ignition source is removed, making it one of the most critical flammability metrics for military and tactical textile products. This article explains the technical principles behind the test, applicable standards such as GB/T 5455 and ISO 15025, sample requirements, step-by-step test procedures, and typical acceptance criteria for flame-retardant camouflage nets.

Technical Overview

Afterflame time is the period during which a material continues to burn with a visible flame after the ignition source has been withdrawn. For camouflage nets, this parameter is a decisive indicator of flame-retardant performance, because nets are frequently deployed near vehicle exhaust systems, generators, cooking fires, and pyrotechnic devices. A net that sustains flaming combustion after brief ignition exposure can fail catastrophically in the field, destroying concealment, igniting surrounding vegetation, and endangering personnel and equipment.

In a standard vertical flammability test, afterflame time is evaluated together with two companion metrics: afterglow time, which measures how long the specimen continues to glow without flame after flaming ceases, and damaged length, which measures the extent of charring or destruction along the specimen. Together, these three parameters define whether a camouflage net material meets flame-retardant requirements.

• GB/T 5455 — Textiles, burning behaviour, vertical method for determining damaged length, afterflame time, and afterglow time.
• ISO 15025 — Protective clothing, flame spread testing of vertically oriented specimens.
• FAR 25.853 — Vertical flame test methodology frequently referenced for ignition exposure duration.
• Military camouflage net procurement specifications, which typically impose afterflame limits on base fabric, coating, and garnish materials.
• GB/T 5454 — Limiting oxygen index (LOI) testing, commonly used as a complementary screening method for flame-retardant finishes.

Testing Samples

Because a camouflage net is a multi-component assembly, samples must be selected to represent every combustible layer and element of the finished product. Test specimens are generally cut from production material so that test results reflect the actual delivered flame-retardant performance.

Base Netting Fabric

The base fabric is typically a woven or knitted polyester or nylon mesh. Specimens are cut in both the lengthwise and widthwise directions, since flame propagation behavior differs between yarn systems. Both uncoated and finished base fabric may be tested to isolate the contribution of the flame-retardant treatment.

Coated and Laminated Materials

Many camouflage nets carry PVC, PU, or acrylic coatings for waterproofing, colorfastness, and radar-scattering performance. Coated composite specimens must be tested in their final laminate construction, because coating weight and plasticizer content significantly influence ignition and afterflame behavior.

Garnished and Masking Components

Attached garnish strips, foliage simulants, and binding tapes are cut and tested individually. These thin, high-surface-area elements often present the greatest ignition risk in the finished net and are subject to their own afterflame limits.

Finished Net Sections

Where specifications require it, representative coupons containing netting, coating, stitching, and garnish in their assembled configuration are tested to verify the interaction between components, including whether the base fabric re-ignites from burning garnish.

Testing Items

The core scope of a camouflage net afterflame time test program includes the following measured parameters and observations:

• Afterflame time, recorded in seconds from the moment the ignition flame is removed until visible flaming extinguishes completely.
• Afterglow time, recorded in seconds from the cessation of flaming until all incandescent glowing ceases.
• Damaged length, the maximum extent of charring or destruction measured in millimeters along the specimen.
• Ignition observations, including surface flash, melting behavior, hole formation, and specimen shrinkage.
• Flaming drips and molten debris, including whether falling material ignites an indicator medium placed beneath the specimen.
• Optional supplementary items such as limiting oxygen index, smoke density, and flame spread rate, depending on the procurement specification.

For materials intended to retain flame retardancy through service life, afterflame time testing is frequently repeated after a defined number of laundering cycles or artificial weathering exposures to verify durability of the treatment.

Testing Methods

Specimen Preparation and Conditioning

Following the vertical method of GB/T 5455, specimens measuring 300 mm by 80 mm are prepared, normally five specimens in the lengthwise direction and five in the widthwise direction for each material. All specimens are conditioned in a standard atmosphere of 20 ± 2 °C and 65 ± 4 % relative humidity for at least 24 hours before testing, in accordance with GB/T 6529. Specimens that have undergone laundering or weathering pre-treatment are conditioned after the pre-treatment is completed.

Apparatus

Testing is performed in a vertical flammability tester consisting of an enclosed, draft-shielded chamber fitted with the following components:

• A vertical specimen holder with pointed retaining pins that secure the specimen without shielding its exposed face or lower edge.
• A gas burner supplied with propane or butane, adjustable to a standard flame height of 40 ± 2 mm.
• Precision timers, either automatic or manually operated, for recording afterflame and afterglow durations.
• Marking threads and small weights used to determine the extent of damage along the specimen.
• A calibrated scale or ruler for measuring damaged length to the nearest millimeter.
• An exhaust system for safely removing combustion products between tests, with ventilation switched off during measurement.

Test Procedure

The vertical method proceeds through the following steps for each specimen:

• Mount the conditioned specimen vertically in the holder, ensuring it hangs freely without wrinkles or tension distortion.
• Position the burner so that the flame impinges on the center of the specimen lower edge, with the burner outlet approximately 20 mm below the bottom edge.
• Adjust the gas flame to 40 ± 2 mm in height and allow it to stabilize before ignition.
• Apply the ignition flame to the specimen for the specified duration, typically 12 seconds under GB/T 5455.
• Withdraw the burner and immediately start the timers; record afterflame time when visible flame extinguishes and afterglow time when glowing ceases.
• Observe and record any melting, dripping, or flaming debris, noting whether drips continue to burn after falling.
• After the specimen cools, measure the damaged length from the original lower edge to the furthest point of char or destruction, using the marking threads as a guide.
• Repeat the procedure for all remaining specimens, replacing any specimen in which flaming does not occur with a spare specimen as permitted by the standard.

Expression of Results

Individual and mean values are reported for afterflame time and afterglow time to the nearest 0.1 second, and for damaged length to the nearest millimeter. Many military specifications judge compliance on the maximum single-specimen value rather than the mean, so all individual results must be documented. The test report also states the standard applied, specimen direction, pre-treatment history, and all behavioral observations such as drips, shrinkage, or surface flash.

Acceptance Criteria

While exact limits are defined by the governing procurement specification, typical flame-retardant requirements for camouflage net materials are:

• Afterflame time not exceeding 5 seconds, with some specifications permitting up to 15 seconds for specific components.
• Afterglow time not exceeding 5 seconds for garnish and base fabric, or up to 30 seconds for certain coated materials where glow does not propagate damage.
• Damaged length not exceeding 100 to 150 mm on the 300 mm specimen.
• No flaming drips or molten debris that ignite material below the specimen.
• Limiting oxygen index of 28 percent or higher where LOI is specified as a screening requirement.

Applications

Afterflame time testing serves several distinct purposes across the camouflage net product lifecycle:

• Military procurement and acceptance testing, where certified afterflame results are a mandatory element of batch conformance documentation.
• Research and development of flame-retardant finishes, coatings, and inherently flame-resistant fibers, guiding formulation optimization.
• Production quality control, verifying that treatment concentration, coating application, and curing processes remain within validated limits.
• Durability qualification, confirming that flame retardancy survives laundering cycles, UV exposure, and field weathering over the net service life.
• Civil and commercial applications, including hunting blinds, wildlife observation hides, tactical training facilities, and emergency camouflage screening where ignition safety is required.

FAQ

What is afterflame time in camouflage net testing?

Afterflame time is the number of seconds a specimen continues to burn with a visible flame after the standardized ignition source is removed. It directly quantifies the self-extinguishing capability of the flame-retardant treatment applied to the net materials.

Which standards apply to camouflage net afterflame testing?

GB/T 5455 is the primary vertical flammability method for measuring afterflame time, afterglow time, and damaged length of textile specimens. ISO 15025 provides an internationally harmonized vertical procedure, and military procurement specifications for camouflage nets impose their own numerical limits on these results.

How many specimens are required?

A standard test set consists of five specimens in the lengthwise direction and five in the widthwise direction for each material, all conditioned to the standard atmosphere before ignition. Additional spare specimens are prepared in case any specimen fails to ignite during testing.

What is the difference between afterflame time and afterglow time?

Afterflame time covers the period of visible flaming combustion after the ignition source is withdrawn, while afterglow time covers the subsequent period of flameless incandescent glowing. Both are recorded separately because a material can stop flaming quickly yet continue to smolder destructively.

How is damaged length measured?

After the specimen has cooled, the maximum extent of charring or destruction is measured from the original lower edge, where the flame was applied, to the highest point of damage along the specimen length. Marking threads help identify the boundary of the damaged zone.

Can finished nets be tested instead of material coupons?

Yes. Where the specification requires it, coupons cut from finished net sections containing base fabric, coating, stitching, and garnish in their assembled state are tested. This verifies component interactions, such as whether burning garnish can propagate flame to the base netting.