Flammability Tests -5.
Flammability Test Methods:
BS 5852 : 1990
This defines the actual test method whereby a specially constructed test rig is designed to form a simulated chair, as described in EN 1021. The foam used is not specified.
Of the eight ignition sources, the most frequently used are Ignition Source 0 (cigarette), Ignition Source 1 (butane flame/simulated match) and Ignition Source 5 (Crib 5). Moving up the ignition source scale, the heat intensity roughly doubles as compared to that of its predecessor.
The requirements for the cigarette and match tests are the same as those detailed under EN 1021, although the match application time was previously 20 seconds before the European Norm was introduced.
The Ignition Source 5 test is more rigorous due to the increased intensity of heat which is generated from the wooden crib structure. Alcohol is added to the small piece of lint at the bottom of the crib which is then placed on the test rig and ignited within 2 minutes. For a pass to be recorded, all flaming should cease within 10 minutes.
BS 7176 : 1995
BS 7176 is a performance standard based on BS 5852, but with three additional parameters:-
(i) Watersoak procedure
(ii) Predictive "Worst Case" testing
(iii) Hazard categories
This procedure is defined precisely in BS 5651 : 1990 Clause 3, but in simple terms requires that a fabric be soaked in water and dried prior to testing. This is done because chemically treated material may be adversely affected by watersoaking and its additional flame retardant characteristics may be greatly reduced or completely eliminated.
Predictive worst case testing
Here the foam used on the test rig is 35kg/m3 High Resilient (HR) foam (not CMHR foam). This has been adopted as a 'worst case' foam on the assumption that the vast majority of manufacturers use Combustion Modified foam which gives better flammability performance.
BS 7176 also helps to identify varying 'hazard' categories which are linked directly to the ignition source used for testing. There are four categories:-
|Medium Hazard||High Hazard||Very High Hazard|
|Typical Examples of usage||Offices,||Hotel Bedrooms||Sleeping accomodation in certain hospital wards and in certain hostels.||Prison cells|
|Colleges,||Public Buildings||Offshore installations|
|Day Centres,||Places of Public entertainment|
|Bars and Casinos|
|1. If a particular premise in the Low Hazard area is used for sleeping purposes then consideration should be given to specifying a higher performance level.|
|2. Upholstered furniture which is ordinarily intended for private use in a dwelling is subject to Government Regulations.|
Typical examples of end usage are indicated by BS 7176 so that the user (and fire officer) knows what specification of fabric is required where. Classifications cover low, medium, high and very high hazard categories with offices coming in the lowest risk category and public buildings, hotels, restaurants, etc being labelled medium hazard. However, it is important to note that these are guidelines only and fire officers and specifiers alike can demand higher standards; this is often true of office environments where "Medium Hazard" fabrics are increasingly preferred.
BS 476: Part 7 (1997)
This standard assesses the flammability performance of flat materials, composites or assemblies, which are used as the exposed surfaces of walls or ceilings. Hence this is the standard which is applied to vertical surface or panel fabrics. The spread of flame along the surface of a specimen held in a vertical position is determined and the subsequent classification system is based on the rate and extent of flame spread.
The test equipment consists of a vertically mounted radiation panel, supplied with a gas-air mixture, together with a specimen holder and pilot flame arrangement mounted to one side. The specimen holder swivels so that it is located at 90o to the face of the radiation panel during the test.
The fabric sample is exposed to the radiation panel for 10 minutes (or until the flame has reached a reference line drawn at 825mm - whichever occurs first) and for the first minute a pilot flame is applied to the bottom corner of the sample. During the test, the time taken for the flame to reach various reference marks is noted, along with the extent of flame spread at 1.5 minutes and at the end of the test. A minimum of six and a maximum of nine samples are tested and are classified according to the performance results shown in the table below.
|Classification of spread of flame|
|Classification||Spread of flame at 1.5 min.||Final spread of flame|
|Limit (mm)||Limit for one specimen in sample (mm)||Limit (mm)||Limit for one specimen in sample (mm)|
|Class 4||Exeeding the limits for class 3|
Vertical Surface Test
The Vertical Surface Test has been specifically devised by Interface Fabrics to assess the flame retardancy of panel systems in typical installation conditions. It has not been formally adopted under national or international legislation, but is the test we are seeking to promote and advocate as being better indicative of how a panel structure is likely to react in a fire.
The test utilises the standard test rig and ignition sources as per EN 1021 which is the standard for upholstered furniture. An "L" shaped construction in this instance simulates a panel in direct contact with its base.
For testing purposes a typical panel construction consists of a soft wood frame with plywood frontage covered in 2mm HR foam. The panel fabric to be tested is then clipped around the panel and positioned the test rig. The base is constructed of chipboard covered in laminate to simulate a desk top. The vertical surface test also includes a watersoak procedure for the fabric.
The ignition sources used and the length of time for which they are applied are identical to those for testing upholstered furniture, ie. Ignition Source 0 (cigarette), Ignition Source 1 (match). The pass criteria are also the same.