Flammability of Vertically Oriented Textile Fabrics and Fabric Assemblies Subjected to a Small Igniting Flame

BRITISH STANDARD BS5438:1976

Methods of test for Flammability of vertically oriented textile fabrics and fabric assemblies subjected to a small igniting flame

UDC677.017.56:536.468 BS5438:1976

Cooperating organizations

The Fibres, Yarns and Fabrics Standards Committee, under whose supervision this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations:

Association of Jute Spinners and Manchester Chamber of Commerce and Manufacturers Industry — Ticking Suppliers’ Committee British Man-made Fibres Federation* Ministry of Defence* British Railways Board Narrow Fabrics Federation British Textile Employers’ Association* Retail Trading Standards Association Consumer Standards Advisory Committee of Incorporated BSI* Textile Institute* Department of Industry* Warp Knitters Association International Wool Secretariat* Wool Textile Delegation Knitting Industries Federation

The organizations marked with an asterisk in the above list, together with the following, were directly represented on the committee entrusted with the preparation of this British Standard:

Apparel and Fashion Industries Association Lambeg Industrial Research Association Association of Heavy Textile Proofers Leather Cloth and Coated Fabrics British Burn Association Manufacturers’ Association British Lace Federation Medical Research Council British Resin Manufacturers’ Association North Yorkshire Fire Brigade British Throwsters’ Association Royal Society for the Prevention of Accidents Chemical Industries Association Soap and Detergent Industries Association Department of the Environment Textile Research Council Department of the Environment — Fire United Kingdom Antimony Oxide Research Establishment Manufacturers’ Association Department of Health and Social Security Greater Manchester Council Fire Service Home Office

This British Standard, having been prepared under the directionof the Fibres, Yarns andFabrics Standards Committee, was published underthe authority ofthe Boardof BSI on 30 November1976 Amendments issued since publication

The following BSI references 3595 April1981 Indicated by a sideline in the margin relate to the work on this standard: Committee reference FBT/19 Draft for comment 74/35997 DC and draft for approval76/35357

ISBN 0 580 092992 BS5438:1976

Contents

Page Cooperating organizations Inside front cover Foreword ii Section 1. General 1 Scope 1 2 References 1 3 Definitions 1 Section 2. Information common to methods1,2 and 3 4 Conditioning and testing 1 5 Health and safety of operators 2 6 Apparatus 2 7 Control of flame size 2 8 Room ventilation 2 Section 3. Methods of test 9 Test1 4 10 Test2 5 11 Test3 7 Appendix A Notes for users of the standard 10 Appendix B Proposed criteria of acceptance 17 Figure 1 — General arrangement of apparatus 3 Figure 2 — Burner 4 Figure 3 — Position of burner 4 Figure 4 — Frame and pin arrangement for tests1 and2 6 Figure 5 — Frame, pin and trip thread arrangement for test 3 8 Figure 6 — Scheme of testing and possible fabric requirements 10 Table 1 — Specimen requirements (in assemblies, per layer) for each surface tested 11 Publications referred to Inside back cover

Foreword

The methods of test given in this standard will supersede those given in BS2963 “Tests for the flammability of fabrics” and BS 3119 “Methods of test for flameproof materials” and have been prepared following a comprehensive research programme and a series of inter-laboratory trials. BS2963 and BS3119 will be withdrawn in due course. A background paper giving some details of the research project and the inter-laboratory trials was published in the February1975 issue of “Textile Institute and Industry”. A second paper giving information on the interpretation and application of the methods is given in the September1976 issue of the same journal. Attention is drawn to these background papers, to Appendix A, which gives notes to users of the standard including the relationship between the tests, and to Appendix B, which gives information on the setting of performance levels. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application.

Compliance with a British Standard does not of itself confer immunity from legal obligations.

Summary of pages

This document comprises a front cover, an inside front cover, pagesi andii, pages1 to18, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. ii © BSI 11-1999 BS5438:1976

Section 1. General 3.5 duration of flaming 1 Scope time for which the supported specimen continues to This British Standard specifies test methods for flame after extinction of the butane flame. This observing and measuring aspects of the measurement is only made when the flaming ceases flammability (when subjected to a small igniting due to the behaviour of the fabric and not because flame) of vertically oriented textile fabrics, flame has reached the edge of the specimen specimens being either a single layer or an assembly 3.6 of two or more layers. These aspects are relevant to duration of afterglow apparel fabrics and to those textile fabrics which time for which the specimen continues to glow after will be held loosely in an essentially vertical extinction of flaming or of the igniting flame, position, for example curtains drapes. whichever is the later. This measurement is only The results may not apply to situations where made when glowing ceases due to the behaviour of there is restricted air supply or prolonged the fabric and not because glowing has reached an exposure to large sources of intense heat as in edge of the specimen, other than the lower edge a conflagration. 3.7 NOTEThe scope has been limited to those fabric end uses tested in inter-laboratory trials but the tests may be used to flame application time assess the behaviour of fabrics or assemblies intended for other the time for which the igniting flame is applied to end uses, provided that the information gained is understood to relate to the fabric or assembly only. the specimen, controlled to an accuracy of± 0.2s for times up to8s and± 0.5s for times of10s or more 2 References 3.8 The titles of the publications referred to in this minimum ignition time standard are listed on the inside back cover. the minimum flame application time required to cause ignition 3 Definitions For the purposes of this British Standard the Section 2. Information common to following definitions apply. methods1, 2 and3 3.1 4 Conditioning and testing ignition 4.1 Conditioning and testing atmospheres. An flaming of the specimen for a period of1s or more atmosphere having a temperature of15°C to25°C after extinguishing of the butane flame, unless and relative humidity55% to65% shall be used for otherwise specified in performance requirements the conditioning of specimens. For testing, an 3.2 atmosphere substantially free from draughts and glowing having a temperature of15°C to30°C and relative combustion of a material in the solid phase with humidity20%to65%shall be used. emission of light from the surface 4.2 Conditioning and testing of specimens. 3.3 Subject the specimens to be tested to the flaming debris atmosphere for conditioning for24h. If the test is not carried out immediately after conditioning, material separating from the specimen during the place the specimen in a sealed container until the test procedure and falling below the initial lower start of the test. Begin testing each specimen edge of the specimen and continuing to flame as it within3min of removing it from either the falls conditioning atmosphere or the container. 3.4 hole a break in the fabric at least2mm× 2mm in size caused by glowing or flaming. If the hole is crossed by any material it should be described as discontinuous

5 Health and safety of operators 6.5 A mounting frame for supporting the test frame. There is a considerable risk with these tests and 6.6 A timer designed to start (preferably suitable precautions should be taken. Between automatically) at the end of the flame application tests, the atmosphere of the testing-room, which time, fitted with a manual stop button and should be of adequate dimensions to avoid operating to an accuracy of0.2s or better. endangering the health of operators, should be 6.7 Additional apparatus as specified in the cleared of smoke and fumes by an extractor fan or appropriate clauses of this standard. other means of ventilation. It should be ensured that the desired atmosphere for testing is restored. 7 Control of flame size Control the rate of flow of butane so that, with the 6 Apparatus burner tube vertical, the height of the flame A general arrangement of the test apparatus is is45± 2mm. Then verify that, with the burner tube given in Figure 1 which shows the test3 pin frame horizontal, the horizontal reach of the flame in position. is23± 2 mm. Extinguish the flame and then return The following apparatus is required. the burner to its horizontal position as shown in Figure 3. Ensure that the horizontal distance from 6.1 A testing room equipped with an extractor fan or the end of the burner to the nearest face of the fabric other means of ventilation and capable of providing is17± 1 mm (see Figure 3). This can be achieved, the atmosphere for testing defined in clause4. It is for example, by means of a wire spacer attached to strongly recommended that the testing room be the burner with subsequent use of a mechanical stop divided into two parts, the inner one for carrying out device. the tests being of a minimum volume of4m3 and of NOTEIt is recommended that the vertical flame height and a minimum height of2m and easily viewed from horizontal reach of the flame should be checked, and if necessary the outer part in which control equipment would be adjusted, at least once per day. situated. 6.2 A supply of commercial butane complying with 8 Room ventilation the requirements of BS4250. Before any specimen is tested, ventilate the testing 6.3 A horizontal-tube burner1) of3mm bore and room or inner part of a divided room, if present, to with the dimensions as shown in Figure 2. The axis ensure adequate oxygen supplies for the test, then of the burner shall be located18mm above the level allow adequate time for air movement to cease after of the bottom row of pins on the frames specified stopping fans or other means of ventilation. in6.4. The burner shall be equipped with means for controlling the rate of gas flow and may also be equipped with means for igniting the gas by an electric spark and for automatically governing the duration of gas flow. 6.4 A test frame with horizontal pins round each edge at50mm intervals, each at such pins being50mm projecting length× 1.83mm diameter with a stub7mm from the tip (see Figure 3). The frame dimensions shall be as specified in the appropriate clauses of this standard.

1) A burner complying with the requirements of this standard is available from James H. Heal & Co. Ltd., Richmond Works, Halifax, West Yorkshire, HX3 6EP and from Shirley Institute, Didsbury, Manchester, M20 8RX.

2 © BSI 11-1999 BS 5438:1976

Figure 1 — General arrangement of apparatus

Figure 2 — Burner

Section 3. Methods of test A rectangular test frame as shown in Figure 4, fitted with two vertical rows of pins150mm apart and 9 Test1 two horizontal rows of pins200mm apart, which can be readily turned through a horizontal axis 9.1 Principle. A wide vertical strip of the fabric or about its centre. (See also6.4.) assembly is taken, and a specified small butane flame is applied to the face of the strip for prescribed 9.3 Preparation of specimens. Prepare at least times. The minimum flame application time is six specimens each measuring220mm× 170mm, found that causes ignition (see clause3) of the three with the longer dimension in the length specimen. direction of the fabric or assembly, three in the width direction. 9.2 Apparatus. The following apparatus, together with apparatus specified in clause6, is required. 9.4 Conditioning of specimens. Condition specimens as described in clause4.

Figure 3 — Position of burner

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9.5 Mounting of specimen. Mount the specimen 9.8.2 The criterion for ignition. vertically on the pins of the test frame, with 9.8.3 Whether or not ignition occurs. If it does, the a170mm edge horizontal, so that it extends10mm minimum flame application time for ignition for beyond the pins at each edge and remains each direction of the material for each face tested. reasonably flat and stationary when mounted. Push 9.8.4 Details of any deviation from the specified test the specimen onto the pins until it reaches the procedure. stubs. Then place the test frame and specimen on the mounting frame unless the specimen was 10 Test2 mounted with the test frame in place. 9.6 Procedure. Proceed in the following way. 10.1 Principle. A wide vertical strip of the fabric or assembly is taken and a specified small butane a) To the outer face of a specimen mounted with flame is applied to the face of the strip for a the length direction of the material vertical, prescribed time. The extent of vertical and apply the butane flame for a duration of2s. Stop horizontal spread of flame is observed. Flaming the timer by means of the manual stop button debris behaviour may be described and the duration when the fabric ceases to flame, and note whether of flaming and afterglow and extent of hole ignition, as defined in clause3 or in an formation may be measured. appropriate performance standard, has taken place. For fabrics in which any part of any hole or any part of the lowest boundary of any flame reaches the If ignition did not occur, and if the state of the upper edge or either of the vertical edges, specimen permits, turn the frame and specimen assessment by test2 will not be adequate and test3 through180 in a vertical plane and repeat but ° should be used. with a flame application time of3s. 10.2 Apparatus. The following apparatus, together If the specimen did not ignite, repeat again but with apparatus specified in clause6, is required. with fresh specimens as appropriate and with flame application times of4,6,8 and10s until A rectangular test frame as shown in Figure 4, fitted the shortest of these times, if any, is found that with two vertical rows of pins150mm apart and causes a specimen to ignite. two horizontal rows of pins200mm apart. (Seealso6.4.) b) Repeata) but starting with a fresh specimen and at one time interval down the sequence of 10.3 Preparation of specimens. For each face to flame application times from the longest be tested, prepare six specimens each application time used ina) (unless this is2s, in measuring220mm× 170mm, three with the which case start again at2s) and with the longer dimension in the length direction of the fabric direction of the material at180° to its direction at or assembly and three with the longer dimension in the corresponding time ina). If the result differs the width direction. by2s or more from the result ofa) repeat once 10.4 Conditioning of specimens. Condition more and report all values. specimens as described in clause4. c) Repeata) andb) using specimens with a width 10.5 Mounting of specimen. Mount the specimen direction of the material vertical. vertically on the pins of the test frame with 9.7 Other face of the material. For some fabrics a170mm edge horizontal so that it extends10mm or multilayer assemblies it may be necessary to test beyond the pins at each edge and remains both faces. With the inner face of the specimen reasonably flat and stationary when mounted. Push towards the igniting flame, repeata),b) andc) the specimen onto the pins until it reaches the of9.6. stubs. Then place the test frame and specimen on the mounting frame unless the specimen was 9.8 Test report. Attention is drawn to the form of mounted with the test frame in place. report sheet suggested in Appendix A. The test report shall begin with the following statement: “The results may not apply to situations where there is restricted air supply or prolonged exposure to large sources of intense heat as in a conflagration”.

The report shall state the information given in9.8.1 to9.8.4. 9.8.1 That the test was performed in accordance with this standard.

g) if ignition occurs and, provided that neithera) norb) occurs, the maximum horizontal extent of any hole and the maximum vertical extent from the lowest point of the lowest hole to the highest point of the highest hole that is formed, measured in situ after cessation of any afterglow. Repeat twice, making three replicates in all, in each direction for each face tested, one of which is rotated through180° relative to the other two. If ignition does not occur in any of the specimens but a hole is formed, use a flame application time of2s to test three further specimens and record whether a hole is formed. If a hole is formed when a flame application time of2s is used, measure and record the maximum horizontal extent of any hole and the maximum vertical extent from the lowest point of the lowest hole to the highest point of the highest hole that is formed, measured in situ after cessation of any afterglow. 10.7 Test report. Attention is drawn to the form of report sheet suggested in Appendix A. The test report shall begin with the following statement: “The results may not apply to situations where there is restricted air supply or prolonged exposure to large sources of intense heat as in a conflagration”. The report shall state the information given in10.7.1 to10.7.4 (unless not required by the performance specification). 10.7.1 That the test was performed in accordance Figure 4 — Frame and pin arrangement for with this standard. tests1 and2 10.7.2 The flame application time. 10.7.3 For each specimen the following information 10.6 Procedure. Apply the igniting flame for10s shall be given: unless some other flame application time is specified in a performance specification. a) whether, for any flame, any part of its lowest boundary reached the upper edge or one of the Observe and record the following information: vertical edges; a) whether, for any flame, any part of its lowest b) whether a hole developed which extended to boundary reaches the upper edge or one of the the upper edge or one of the vertical edges; vertical edges of the specimen; c) the separation of any flaming debris; b) whether a hole develops which extends to the upper edge or one of the vertical edges of the d) the duration of flaming; specimen. e) the duration of afterglow; If required by the performance specification, f) whether flowing reached the upper edge or one measure and record the following information: of the vertical edges; c) the separation of any flaming debris; g) if appropriate, the maximum vertical and d) the duration of flaming; horizontal extent of any hole that is formed, whether it is continuous or discontinuous, using e) the duration of afterglow; a10s flame application time; f) whether glowing reaches the upper edge or one of the vertical edges of the specimen;

6 © BSI 11-1999 BS5438:1976

h) if appropriate, the maximum vertical and 11.3 Preparation of specimens. For each face to horizontal extent of any hole that is formed, be tested (see also provision for pretesting in11.6) whether it is continuous or discontinuous, using prepare at least six specimens each a2s flame application time. measuring670mm× 170mm, three with the 10.7.4 Details of any deviation from the specified longer dimension in the length direction of the fabric test procedure. or assembly and three with the longer dimension in the width direction. If it is necessary to join pieces of 11 Test3 fabric to make up specimens of the required dimensions this should be done by means of metal 11.1 Principle. A wide vertical strip of the fabric or staples without any overlapping of the fabric. Do not assembly is taken and a specified small butane join more than three pieces to form any one flame is applied to the face of the strip for a specimen. Provision is made for testing short and prescribed time. The rates of vertical and horizontal narrow specimens in11.8 and11.10. spread, of flame are measured. Flaming debris 11.4 Conditioning of specimens. Condition the behaviour may be described and the duration of specimens as described in clause4. flaming and of afterglow may be measured. 11.2 Apparatus. The following apparatus, together 11.5 Mounting of specimen. Mount the specimen with apparatus specified in clause6, is required. vertically on the pins of the test frame so that the surface that will be outermost while being used in 11.2.1 A rectangular test frame as shown the intended way faces the igniting flame, unless it inFigure 5, fitted with two vertical rows of is not known which surface will be outermost (in pins150mm apart and two horizontal rows of which case the surface which is shown to spread pins650mm apart so arranged that the pins form a flame the faster faces the igniting flame), or as rectangle with the longer dimension vertical. The otherwise specified, with a170mm edge horizontal frame may be provided with means for including a so that it extends10mm beyond the pins at each horizontal row of pins350mm above the bottom edge, and remains reasonably flat and stationary horizontal row for short specimens (see11.8) and when mounted. Push the specimen onto the pins two vertical rows whose horizontal separation may until it reaches the stubs. Then place the test frame be adjusted from20mm to150mm for narrow and specimen on the mounting frame unless the specimens (see also6.4 and 11.10). When full size specimen was mounted with the test frame in place. specimens are being tested these additional pins 11.6 Pretesting to find which surface of the shall not be in position. material spreads flame the faster. Omit 11.2.2 Cotton trip threads (46tex) horizontally pretesting if both faces are required to be tested or located at300mm and600mm above the nominal if the face to be tested is specified in the level of application of the butane flame (45mm performance specification. above the lower edge of the specimen) and vertically located at75mm on either side of the centre line Cut two specimens370mm× 85mm in the same and mounted so that they are just inside the pins direction, which may be any direction of the fabric. With only the trip thread at300mm in operation (see Figure 5). Each thread traverses the specimen and with a65mm pin separation between vertical twice, at distances5 mm and15mm from the rows of pins, test the two specimens in turn with surface facing the igniting flame. different surfaces towards the igniting flame. In this 11.2.3 Three timers operating to an accuracy of0.2s way determine the surface of faster flame spread. or better, arranged so that all are started simultaneously when the igniting flame is applied to the specimen. The timers are stopped (one each) by severance of the trip threads at300mm and600mm and the third by either of the vertical trip threads.

Figure 5 — Frame, pin and trip thread arrangement for test3

8 © BSI 11-1999 BS5438:1976

11.7 Procedure. Set the trip threads and timers. If trimmings have to be tested by themselves, test Apply the igniting flame for10s unless some other them as if they were single fabrics, with the flame application time is specified in a performance narrower dimension horizontal, specimen width specification. requirements being ignored. This reduces the Observe and record the following information: number of pretest dispositions relevant. Mount specimens on the adjustable rows of vertical pins so a) all trip thread severance times. that the pins just secure the long edges of the If required by the performance specification, trimmings. The procedure is otherwise as described. measure and record the following information: 11.11 Test report. Attention is drawn to the form b) the separation of any flaming debris; of report sheet suggested in Appendix A. The test c) the duration of flaming if20s or less, otherwise report shall begin with the following statement: record as greater than20s; “The results may not apply to situations where d) the duration of afterglow if60s or less, there is restricted air supply or prolonged exposure otherwise record as greater than60s. to large sources of intense heat as in a In the event of afterglow continuing for60s before conflagration”. glowing reaches an edge of the specimen other than The report shall state the information given the lower edge, the test is terminated. in11.11.1 to11.11.4 (unless not required by the 11.8 Modified procedure for materials that do performance specification). not burn extensively or that are scarce. If the 11.11.1 That the test was carried out in accordance material is not expected to burn beyond the300mm with this standard. trip thread or if insufficient material is available to 11.11.2 The flame application time. provide specimens670mm× 170mm, then short 11.11.3 For each specimen the following specimens measuring370mm× 170mm may be information shall be given: used, in which case the optional row of pins350mm above the bottom row is used and the trip thread a) times at which the various trip threads were at600mm is omitted. The procedure is otherwise as severed (use “ns” if trip thread not severed; “x” if described and yields trip thread times for300mm trip thread absent, e.g.when short specimens vertically and75mm horizontally. tested); 11.9 Limitations on use of short specimens. If, b) the separation of any flaming debris; during testing of any short specimen, the trip thread c) the duration of flaming if20s or less. If more at300mm is severed then the normal procedure than20s report>20s; with specimens670× 170mm shall be followed if d) the duration of afterglow if60s or less. If more sufficient material is available. than60s report>60s. 11.10 Modified procedures for narrow fabrics 11.11.4 Details of any deviation from the specified or assemblies. If possible, and always if the test procedure including, if appropriate, details of: specimen is too narrow to be fitted onto the vertical a) length and/or width of specimen; rows of pins when set at20mm, test trimmings as part of the assembly in which they are or will be b) specimens made by joining pieces of fabric. used. (This implies testing in one direction only, if the assembly is in garment form with the trimming attached in one direction only; if in garment form and any part of the trimming is attached with its narrower dimension horizontal, it shall be tested thus; if the assembly is in fabric form and there is sufficient fabric, it shall be tested in both directions.)

Appendix A Notes for users of the standard

Figure 6 — Scheme of testing and possible fabric requirements

10 © BSI 11-1999 BS5438:1976

A.1 The tests The scheme involves three methods of test which may be used either in sequence or individually (see Figure 6) depending, for example, on performance specifications, availability of previous data or evaluation needs. Figure 6 also indicates likely fabric requirements for testing one face of a fabric having an ignition time of10s and the parameters measured in each test. Full details of fabric requirements are summarized in Table 1. It should be noted that assemblies of two or more layers may be tested and that the butane flame is applied above the lower edge to avoid any artifact created by a cut edge. A.2 Apparatus The description of the apparatus in the standard shows the relative positions of specimen, mounting frame, trip threads and ignition source; it does not provide sufficient information to build equipment which will meet the time tolerances specified and be ergonomically satisfactory. Experience gained during development work showed that: a) in test1 it is particularly important to observe carefully any flaming of the specimen after extinction of the butane flame, and measure accurately, without any distraction occasioned by manual control of the butane flame application time, the time at which this flaming ceases; the equipment should provide, within the tolerances specified in the standard, flame application times of2,3,4,6,8 and10s, and also longer times which may be required on occasion; b) the engineering work required to start a number of mechanical timers synchronously and stop them when needed, with the required precision and reliability, could more than outweigh the higher initial cost of electrical timers. Table 1 — Specimen requirements (in assemblies, per layer) for each surface tested Specimen

Clause Number Test number Dimensions Area Comments reference min. max. mm m2 1 9.3 220× 170 6 16 0.23to0.60 Dependent on ignition time and specimen reuse 2 10.3 220× 170 12 0.46 3 11.3 670× 170 6 0.69 3 Pretesting to select a 11.6 370× 85 2 0.07 surface 3 Materials that do not 11.8 370× 170 6 0.38 If flame reaches top burn extensively then as in11.3 3 Materials that are 11.8 370× 170 3 6 0.19to0.38 scarce 3 Narrow fabrics or 11.10 670× 170 3 0.35 If tested as part of a assemblies or wider assembly 670× actual 3 — If tested alone width

The means used to control butane pressure and flow rate should permit easy adjustment of the height of the flame within the specified tolerance, and keep it within the tolerance during a period of use. The final cut-off valve on the gas supply system should be at the end of the non-flexible supply tube nearest to the burner. A heavy gauge flexible tube not exceeding600mm in length or8mm in internal diameter should

be used to connect this valve to the burner. The burner should be mounted so that it can be placed rapidly in a vertical position for checking flame height and then returned to the defined horizontal position. Specimens of different thickness will require the burner to be placed in different positions relative to the test frame.

The relative position of the burner and test frame are specified so as to ensure that the butane flame will impinge on the face of the specimen at a region about45mm above the lower edge of the specimen. To ensure unrestricted movement of combustion products, uniform between different sets of equipment, it is recommended that there be an unrestricted space around the test frame, its immediate supports and the burner extending700mm above the top row of pins,200mm in any direction from the outermost columns of pins and150mm below the bottom row of pins, and that the area below the frame should be covered by a non-combustible debris tray. Some products of combustion are corrosive; the equipment should be, as far as possible, provided with an appropriate protective coating. Other pieces of apparatus possibly sensitive to corrosion should not be left in the same enclosure. The standard does not require a horizontal trip thread150mm above the flame application point, but such a facility may be provided. A.3 Specimen requirements and preparation Before specimens are cut, plan how, as far as possible, all those likely to be required (see Table 1) may be obtained from the sample available by, for example, laying templates of appropriate sizes on the sample. Place a suitable mark, for exampleE, on each specimen in a defined position, to relate specimen orientation to the material (fabric or garment). Suitable defined positions may be warp vertical, wales vertical, or upwards vertical in garment. Additional uncut specimens may sometimes be needed. To prevent delay on such occasions condition all the material and not just cut specimens; indeed, specimen preparation can be carried out at any time during conditioning. In test1, the number of specimens required depends on the minimum ignition time of the fabric or assembly and whether it is possible to use each specimen for two flame applications, as described in the second paragraph of9.6 a). A specimen should not be used for a second flame application if during the first test: a) any sign of damage appears more than halfway up the specimen, or b) any noticeable part of the total flame is due to combustion of the specimen, or c) moisture loss resulting from the first flame application is likely to affect ignition. In test3, a need for pretesting to find which surface spreads flame the faster will require two specimens370mm× 85mm, cut in the same direction. These specimens should be cut in such a way as to leave sufficient material for the main specimens (11.3). This allows diagonal cutting, for pretesting only, without encouraging it. When testing materials that are scarce(11.8) it is generally preferable to use the specified number of specimens, each of370mm length, rather than a smaller number some of which are of the full length(670mm). When preparing specimens from smaller pieces of fabric, the pieces should be arranged so that the joins (one or two) are as near the top of the specimen as possible and each made with four equally spaced staples, unless more are necessary to reduce curling or to hold flimsy fabrics sufficiently flat. A.4 Experimental techniques The quality of experimental technique required will depend to a significant extent on the design of parts of the equipment not specified in this standard. For example, the less automatic the equipment, the greater will be the need for operator skill to achieve the required precision. Some practical points of a general nature are noted ina) tog) below; the operator should refer to the instruction manual for the specific equipment for detailed instructions. a) For reasons of safety, the test equipment should be remote from the butane cylinder, which could be sited advantageously outside the building. In this case a manually-operated valve should be provided just inside the room housing the apparatus. On each occasion the equipment is used, time should be allowed for pure butane to reach the burner jet and thus provide a steady flame. The equipment should be installed and used so that it is not possible for smouldering particles, carried away by the hot gases or falling from the specimen, to come to rest on combustible materials. Protective clothing, fire extinguishers and alarm signals should be available to the operator.

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b) It is important to keep the apparatus clean, both to maintain safety and to ensure that trip threads can move freely round bollards and through guides. It may be useful to clean these working locations by rubbing with a spare length of trip thread. c) It may be easier to mount horizontal trip threads after the vertical threads, slipping the horizontal loop between the vertical threads in each pair. d) On rare occasions it has been noted that, when a horizontal trip thread is severed, a smouldering end may fall away and sever a vertical thread. If this should happen the result for that vertical thread should be disregarded. e) Some grey-state fabrics, for example single jersey knitted fabrics, are liable to curl. This tendency may be reduced by subsequent processing. It is desirable to test this type of fabric in its finished state, since curled edges can have marked effects on flammability behaviour, reducing the actual rate of flame propagation. f) Specimens for tests1 and2 may usually be readily mounted with the frame in the vertical, working position. For test3, specimens may be mounted with the frame horizontal and tapped onto the pins with a wire brush. Assemblies are generally mounted layer by layer, unless already combined. g) Residual material adhering to the pins after testing may be removed with a wire brush, after first crushing solidified lumps of molten material, for example with a pair of pliers. Extinguish any smouldering thread before placing it with other waste thread in a non-combustible container. A.5 Report forms A.5.1 General. It is advisable to use a standard format for expressing results to establish a convention and minimize misunderstanding. The forms given inA.5.2 toA.5.4 are suggested. Reports of minimum ignition times are specific for test1, flames and holes reaching edges and hole dimensions for test2, and trip thread severance times for test3. Both test2 and test3 provide for reports on flaming debris, duration of flaming and afterglow. The report forms for each test list all the appropriate parameters but it is suggested that only the data specifically required in any particular instance be entered. It is possible to derive other data from those listed; deliberately, no provision has been made for such derived data on the report forms. The operator can thus concentrate on observation and recording, free from distraction due to arithmetical operations. Should derived data be relevant, they can be calculated later. The test1 report form is designed for a single criterion for ignition. Because a fabric may be evaluated by reference to two or more criteria of ignition, it may be found useful to enter duration of flaming times in seconds instead of ß or X. The broken diagonal lines in the test1 report form are included to indicate to the operator the sequence of flame application in9.6 a), and are not necessarily for inclusion in the final report. For test3, the first two specimens of any set of three are tested in opposite orientation; the third is tested in the same orientation as the faster burning (t300) of these two.

A.5.2 Test1 report

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A.5.3 Test2 report Report of tests carried out in accordance with BS5438, test method2. The results may not apply to situations where there is restricted air supply or prolonged exposure to large sources of intense heat as in a conflagration.

Specimen reference Flame application time s

Fabric/a ü length Fabric/a ü width Face tested ý ý Garment þ direction Garment þ direction

Specimen number 1E 2G 3E 4F 5D 6F

Flame reached an edge (ß or X)

Hole reached an edge (ß or X) Complete if required by performance specification

Flaming debris (ß or X) Duration of flaming (s)

Duration of afterglow (s)

Maximum vertical extent of hole (mm)

Maximum horizontal extent of hole (mm) If hole formed but no ignition on all 3 replicates in any one direction mark mark ß in box. In this case, hole size dimensions relate to2s flame application time. Deviation (if any) from specified procedure:

a delete what does not apply

A.5.4 Test3 report Report of tests carried out in accordance with BS5438, test method3. The results may not apply to situations where there is restricted air supply or prolonged exposure to large sources of intense heat as in a conflagration.

Specimen reference Flame application time s

Fabric/a ü length Fabric/a ü length Face tested ý ý Garment þ direction Garment þ direction

Specimen number 1E 2G 3Éa 4F 5D 6´a

t300 s

t600 s

tH s Complete if required by performance specification

Flaming debris (ß or X) Duration of flaming (s) (Enter>20s if more than20s duration)

Duration of afterglow (s) (Enter>60s if more than60s duration) Deviation (if any) from specified procedure:

Details of pretest (if any):

NOTEWhere a thread is unsevered insert “ns”. Where a thread was not in place at the start of the test write “x”.

a delete what does not apply.

16 © BSI 11-1999 BS5438:1976

Appendix B Proposed criteria of acceptance

B.1 General This appendix proposes principles on which to decide whether a given performance requirement is satisfied by the test results. In particular, it proposes criteria for tests2 and3 by which to accept or reject a material when the individual results contain one or two “outliers” or “fliers” that show much more hazardous behaviour than the others. The reasoning adopted, following, for example, that of BS476-7, is to choose one acceptance limit for all values except the worst one, and another, more lenient, limit for the worst value. The separation between these limits is based on practical experience. Reproducibility for trip thread severance and ignition time is likely to be better than for other parameters. In this way a reasonable tolerance is allowed for the usual scatter of results, but a grossly bad outlier is cause for rejection of the material. B.2 Minimum ignition time (test1)

If tc is the minimum value specified in a performance specification for the minimum ignition time, the proposed criteria are: a) values should be obtained, for the appropriate direction on the appropriate face of the material, either for two specimens agreeing within2s, or for three or more specimens;

b) the smallest value should exceed tc. B.3 Vertical and horizontal extent of hole (test2)

B.3.1 Vertical extent of hole. If Vc is the maximum value specified in a performance specification for the vertical extent of any hole that is formed, the proposed criteria are: a) values should be obtained for at least three specimens, with the appropriate direction of burning, on the appropriate face of the material;

b) all values except the largest one should be less than Vc;

c) the largest value should be less than mVc, where m is a number, greater than unity, to be chosen on the basis of practical experience. It is suggested provisionally that the arbitrary value m =1.4 be adopted. Thus if, for example, a performance requirement specifies50mm as the greatest vertical extent of any hole, then the criteria allow one hole to be up to70mm long, but the others should be less than50mm.

B.3.2 Horizontal extent of hole. if Hc is the maximum value specified in a performance requirement for the horizontal extent of any hole that is formed, the proposed criteria are: a) values should be obtained for at least three specimens, with the appropriate direction of burning on the appropriate face of the material;

b) all values except the largest one should be less than Hc;

c) the largest value should be less than nHc, where n is a number, greater than unity, to be chosen on the basis of practical experience. It is suggested provisionally that the arbitrary value n =1.4 be adopted. B.4 Time for a specified vertical or horizontal travel of flame (test3)

If tc is the minimum value specified in a performance specification, the proposed criteria are: a) values should be obtained for at least three specimens in the appropriate direction on the appropriate face of the material;

b) all values except the smallest one should exceed tc;

c) the smallest value should exceed ptc, where p is a number, less than unity, to be chosen on the basis of practical experience. Some practical results, and a corresponding suggested value of p, are summarized as follows. In the course of the research leading to the development of the new tests, flame travel times were obtained for a total of17 fabrics, which included single fabrics and two-fabric assemblies (three specimens of each). Of the individual times for a vertical travel of600mm, let t1 be the smallest and t2 the next. For14 fabrics out of17 the ratio t1/t2 was found to be greater than0.75; for eight fabrics the ratio was greater than0.9. The value p =0.75 is therefore suggested as allowing the usual scatter but excluding any seriously bad outlier.

Thus if, for example, a performance specification specifies30s as the minimum time for a specified travel of flame, then the criteria allow a time as short as22.5s for one specimen, but the others should give times exceeding30s. B.5 Inconsistency between tests2 and3 An individual outlier result may bring about an inconsistency between tests2 and3. Consider, for example, the following situation. In test2, suppose that one specimen allows flame to spread to an edge and the other specimens do not. The results show that the material cannot be assessed by reference to test2 alone, and indicate that test3 should be applied for further characterization. In test3, suppose that no specimen causes any trip thread to be severed or burns as far as the position of the upper edge on a test2 specimen. These results indicate that test3 was not necessary after all. To cope with this inconsistency, the following criteria are suggested, following the reasoning of a proposed US standard for general apparel. The second of these criteria, though arbitrary, has the merit that all the results obtained are taken into account, and there is no possibility of selecting a desired result and neglecting the others. a) The material can always be safely assessed by reference to its performance in test3, the test with the larger specimen. b) If it is desired to assess the material by reference to its performance in test2, the propriety of doing so is judged as follows. Six further specimens are tested by test2, in the same direction on the same face and with the same flame application time as the specimen that allowed flame to spread to an edge. If none of these further specimens allows flame to spread to an edge, then the material may be assessed accordingly. If any of these further specimens allows flame to spread to an edge, then the material cannot be assessed by reference to test2 alone. B.6 Duration of flaming (tests2 and3) The results of an inter-laboratory trial showed that this property was very variable for certain fabrics. Some treated cellulose fibre fabrics gave durations of flaming almost always less than1s, but some thermoplastic fibre fabrics gave values ranging (for example) from less than1s to29s for the same fabric tested in the same laboratory. From12 fabrics having only a restricted spread of flame, the durations of flaming in test3 could be grouped as follows: for seven fabrics, almost always less than20s for two fabrics, some less and some greater than20s for three fabrics, almost always greater than20s. These observations are the basis of the dividing line of20s adopted in the reporting of the results of test3. Because of the wide scatter of values found for some fabrics and the near constancy of values (less than1s) found for others, it is not possible to propose any general criteria of acceptance analogous to those inB.2 andB.3.

Publications referred to

BS 476, Fire tests on building materials and structures. BS 476-7, Surface spread of flame tests for materials. BS 4250, Commercial butane and propane.

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