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Textiles F.R. Limited
Flame Retardancy Finishers & Consultants
UKAS
 
BS5852:1990:Source 5
Methods of test for assessment of the ignitability of upholstered seating by smouldering and flaming ignition sources.
Crib 5 Test
Introduction to BS5852:1990: This document contains the test method and flammability requirements for upholstery composites exposed to ignition sources 2 to 7. Each ignition source has twice the calorific output as the one preceding it. Sources 2 & 3 are butane flames (each of greater calorific output than that of the match source described in BS5852:1979). Sources 4 to 7 are wooden cribs ranging in weight from 8.5 grammes (crib 4) to 126 grammes (crib 7) and are illustrated opposite.
A wooden Crib 5 ignition source weighs 17 grammes (+/- 1 gramme) and is composed of 20 sticks of Scots Pine (Pinus Silvestris). In the UK, this is the most frequently used ignition source for testing fabric used in contract furniture. The test rig used is shown below where a crib 5 test is being conducted.

BS5852:1990:Source 5 Procedure: Cover fabric is secured over filling material constituting the seat and back of a small "chair". The test fabric dimensions are 1100mm x 650mm (length x width). Prior to testing, all fabric and filling material is maintained in an air conditioned environment (in which both temperature and relative humidity are controlled) for a specified time. The tests are also conducted within specified temperature and humidity ranges. The ignition source is placed in the centre of the rig. Events occurring after crib ignition are recorded, e.g. time to fabric ignition, cover split, flame extinction. Once all flaming ignition has ceased, the filling material is examined for damage. The test method describes limits to length of time the assembly may burn and to the extent of damage that may be sustained by the filling. The test assembly is assessed against these pass/fail criteria and thereby judged to have complied or failed to comply with the test requirements. Each test is conducted in duplicate. Both replicate test assemblies must satisfy the pass/fail criteria in order to comply with the test requirements.

Filling Material: Ideally, the filling material used in the test should be the same as that used in the finished item of upholstery. In practice, fabric suppliers are unlikely to know what filling material the cover fabric will be used with when the furniture is made up. As a consequence, we conduct most Crib 5 tests using CMHR foam with an approximate density of 35 kg/cubic metre. The filling depth is 75mm.

Pass & Fail Criteria: There are two principle areas considered here, progressive smouldering and flaming ignition. The pass/fail criteria vary depending on which ignition source is used, for this account only those relating to source 5 are described. Considering progressive smouldering first, the fail criteria are;

  • any specimen that displays escalating smouldering combustion so that it is unsafe to continue testing and requires forcible extinction.
  • any specimen that smoulders until it is consumed or that smoulders to the extremities of the specimen.
  • any specimen that produces externally detectable amounts of heat,smoke or glowing 60 minutes after igniting the crib

Considering flaming ignition, the fail criteria are;

  • escalating flaming combustion where it becomes unsafe to continue testing and requires forcible extinction.
  • any specimen which burns until it is consumed within the test duration.
  • any specimen where the flame front reaches the specimen extremities (other than the top of the vertical part) or passes through the full thickness of the composite.
  • any specimen that continues to flame 10 minutes after igniting the crib.
  • debris falling from the test specimen causes an isolated floor fire which burns for more than 10 minutes after igniting the crib
 
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