FR fabrics in the treated arena seems to be having very limited challenge to the instances of Afterglow. However, poor finish of the final FR fabric may not give the intended result and on top of that the situation may become worse if the fabric is purposely made soft with fabric softener. Fabric softeners make the retardance property of the fabric worse by adding an extra layer of fire conductivity- which is in direct contradiction to the intended use. Many a times the fabric is made to last several EN 11612 standards and it is not difficult to control each parameter’s performance. However poor literature and ambiguity on part of the understanding of FR standards can give quite a shocking outcomes even though the standards are controlled to perform during production and FR process.
According to the official “ISO 15025:2000(en) Protective clothing — Protection against heat and flame — Method of test for limited flame spread” document, which explicitly defines the afterglow as:
1. Scope
This International Standard specifies a method for the measurement of limited flame spread properties of vertically oriented textile fabrics and industrial products in the form of single or multi-component fabrics (coated, quilted, multilayered, sandwich constructions, and similar combinations), when subjected to a small defined flame.This test method is not appropriate for materials that demonstrate extensive melting or shrinkage.
2. Terms and definitions
For the purposes of this International Standard the following terms and definitions apply.
2.1 flame application time
time for which the ignition flame is applied to the test specimen
2.2
afterflame time
duration of flame
length of time for which a material continues to flame, under the specified test conditions, after the ignition source has been removed
Note 1 to entry: Afterflame time is measured to the nearest second and afterflame times of less than 1,0 s should be recorded as zero.
2.3
afterglow
persistence of glowing combustion of a material under specified test conditions, after cessation of flaming or, if no flaming occurs, after removal of the ignition source
Note 1 to entry: Afterglow is a continuation of combustion with the evolution of heat and light but without flame. Some materials absorb heat during the flame application and continue to emit this absorbed heat after removal of the igniting flame. This glowing without combustion should not be recorded as afterglow.
2.4
afterglow time
duration of afterglow
time for which a material continues to afterglow, under specified test conditions after cessation of flaming or after removal of the ignition source
Note 1 to entry: Afterglow time is measured to the nearest second and afterglow times of less than 1,0 s should be recorded as zero.
2.5
char
formation of a brittle residue when material is exposed to thermal energy
2.6
debris
material separating from the specimen during the test procedure and falling from the specimen without flaming
2.7
flaming debris
material separating from the specimen during the test procedure and igniting the filter paper
2.8
hole
break in the test specimen of at least 5 mm in any dimension and having a continuous perimeter caused by melting, glowing or flaming
Note 1 to entry: If the hole is crossed by any material it is described as discontinuous.
Note 2 to entry: This International Standard describes the reporting of holes in any separable layer of a multilayer specimen obtained during suface ignition testing [see 8.2.1.3 g) and 10 i)].If we pay attention to the point 2.3 it clearly mentions that any afterglow should not cause any combustion, where Combustion means “the act of burning,”. Thus the lab technician must ensure that they do not overdo the things in order to achieve “no afterglow”.
The Testing method of A1/A2 can be assessed from this explanatory picture by Mr. Martin Lill, Director- International Marketing- Lakeland Industries Inc.
In this tests a sample of fabric (200mm x 160mm) is suspended vertically with the short edges at top and bottom. A small flame is applied to the fabric for 10 seconds and then withdrawn. There are two defined methods:-
· Procedure A applies the flame to the centre of the fabric
· Procedure B applies the flame to the bottom edge of the fabric.
The reaction of the fabric is monitored and assessed according to whether it ignites, continues to burn, melts or drips molten debris. It classifies fabrics as one of three “Index’s” according to the following criteria:-
● Index 1: No burning or melting to a fabric edge / no molten debris / afterglow ≤2 seconds
● Index 2: As Index 1 + no hole formation ≥5mm
● Index 3: As Index 2 + any afterflame must be ≤2 seconds
An important point is that an Index 1 material will not provide protection against any flames or heat (it does allow holing) and must not be worn next to the skin. It must be worn OVER an Index 2 or 3 material, which of course, as they require minimal holing in the test, do provide some protection. Secondary FR Workwear is generally certified as Index 1.
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