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Flame Retardency – “The Inside Story”

Flame Retardency – “The Inside Story”
May 26, 2020

TECHNICAL BULLETIN: Flame Retardency – “The Inside Story”
Date: 24th November 2004

The Standards:
B.S. 3119: 1959 – Withdrawn
B.S. 3120: 1959 – Withdrawn
CP413 – An old Greater London Council Authority (GLC) Regulation, which included clauses about the equipment to be used in the ventilation of buildings, and their fire retardancy. Tests of components were performed by L.S.S. who developed various test methods, as those covered by British Standards were not felt to be appropriate as they were for testing such items as children’s night clothing and soft furnishings. Now not relevant due to demise of GLC.

B.S. 5588: 1989 – Fire Precautions in the design and construction of buildings.

  • Part 9 being the Code of Practice for ventilation and air conditioning ductwork.
  • Section 3 of this includes the following RECOMMENDATION “Surfaces of air filters, attenuators and similar components of ventilating systems exposed to the air flow should be inherently non-flammable or so treated that they retain these qualities throughout their recommended working life. Viscous liquids in air filters should have a flash point of not less than 177 Deg C.

A Test Method for evaluating the compliance of air filters to CP413 was developed by the LSS, and this same standard is used by a current Testing Service of
Stranger Science and Environment. This Test House uses Edition III dated 31.13.1990 of the LSS specification.

The test method looks at:

  • Ignitability – where in the presence of a small flaming ignition
    source, the filter, its housing, fixings etc. may ignite and continue to
    burn but must not spread flame, nor must it produce any flaming
  • Smoke Test – the rate of production and overall amount of smoke
    shall be judged by comparison with a standard, that “if involved in a
    fire all such materials and liquids should generate the minimum
    amount of smoke”.
  • Toxic Gases – “If involved in fire all such materials and liquids should
    generate the minimum amount of toxic gases”, on the basis of their
    chemical composition and measured concentration of toxic gases when
    compared with the H.S.E. guide EH40/91.

UL900: An American Standard written by the Undewriters Laboratory. It has 2 classes within our area of concern:

  • Class 1 – for which filters using glass only media and kevlar thread would conform.
  • Class 2 – for which the pleated medias being used by ourselves conform.

DIN 53438 – Parts 1-3 see attached sheets for detailed information concerning the test methods.
This tests for the reaction of materials to the flame of a gas burner.
There are three classes for this test, which are effectively:

  • Class F1 – the spread of flame does not reach the mark 150mm above the flame
  • Class F2 – the spread of flame takes in excess of 20 seconds to reach the mark 150mm above the flame point on the material.
  • Class F3 – the spread of flame reaches the mark in less than 20 seconds.

The use of Fire Retardant Materials can only be of benefit to all of us. But this has to be tempered with reality.

  • Eliminating the use of cardboard frames to filters is an obvious reduction in flammability and easily achieved.
  • The dust that the air filters are removing will burn and support combustion, admittedly the filter does not have to assist in this burning process.
  • The quantity of material involved is quite minimal, in comparison with the size and quantity of other materials within the buildings, and these materials are likely to be on the plant room side of fire dampers.
  • The use of non-flammable materials is only a recommendation within this standard, which would suggest that if required it must be specified as a particular requirement in a specification, i.e. the recommendation is to be met, and not just the equipment shall conform to BS5588: 1989 etcÔǪ., at the Consultant specification stage..
  • The F6 grade pleats meets Class 2 UL900.
  • The F6 grade pleats meets Class F1/F2 of DIN 53438 Part 3 (Copy attached)
  • The G4 grade pleats meets Class 2 of UL900.

DIN 53438 PART 1
Testing of Combustible materials

General remarks

  1. Scope and application
    The test of products are suitable to control and compare the consistency of
    products regarding the reaction against the flame of a burner. The test
    results give only a rough indication of flame reaction if the testing
    conditions are different.
  2. Brief description of the testing procedures
    The flame of a gas burner is applied to a horizontally held test filter;
    – at the bottom edge (K / DIN 53 438 part 2) of the sample, and
    – to the body of the rest of the test material itself (F / DIN 53 438 part 3).
    It is to be determined if and in what length of time the flamepeak reaches
    a certain measurement mark on the test sample.

Note: Due to international experience it is correct to say that the results of
testing combustible materials in fixed conditions in research laboratories
cannot be taken as proven evidence of a general fire risk.
Conclusions referring to the test results of DIN 53 438 must not be valid in
general if the testing conditions are different from the above mentioned