Fire and Polymers II - ACS Publications - American Chemical Society

Chapter 3 7

Combustion Behavior of Upholstered Furniture Tested in Europe Overview of Activities and a Project Description

Downloaded by NATL UNIV OF SINGAPORE on May 5, 2018 | https://pubs.acs.org Publication Date: July 21, 1995 | doi: 10.1021/bk-1995-0599.ch037

Björn Sundström Sveriges Provnings-och Forskningsinstitut, Swedish National Testing and Research Institute, Fire Technology, Box 857, S-501, 15 Borås, Sweden The European Commission has prepared a draft directive on the fire behaviour of upholstered furniture. Two essential requirements on fire properties are given. These are for ignition resistance and burning behaviour. Four levels of ignition resistance are defined; ignition by cigarette, match flame, 20 g and 100 g of newspaper. CEN, the European Committee for Standardization, has almost finalized the standards for cigarette and match flame. Work is in progress to develop the needed test standards for the newspaper sources. The second essential requirement addresses the problem when the furniture burns and people must be able to escape. However, required standards and evaluation techniques are not available. Therefore the Commission has funded the CBUF-programme to provide for technical solutions of testing and evaluation. CBUF, Combustion Behaviour of Upholstered Furniture, started in 1993. The budget is approximately 2.8 million dollars. Fire experts from 8 European countries co-operate. The project manager is from DBI, Danish Institute of Fire Technology, Denmark, while SP, Swedish National Testing and Research Institute, is responsible for the technical co-ordination. CBUF assumes that evaluation of the burning behaviour is carried out by the cone calorimeter (ISO 5660) for small scale testing and, as reference, the furniture calorimeter (NT FIRE 032) for large scale. Reliable test protocols are developed, hundreds of tests are performed and fire models that can predict the relevant hazard parameters are created. The European Commission has prepared a draft directive on the fire behaviour of upholstered furniture . The objective is to promote European harmonization of re quirements and test methods that offer a high and consistent safety level. Surveys 1

0097-6156/95/0599-0609$12.00/0 © 1995 American Chemical Society Nelson; Fire and Polymers II ACS Symposium Series; American Chemical Society: Washington, DC, 1995.

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of European statistics show that a major cause of fire fatalities is associated with burning of upholstered furniture . Ignition by smokers' materials are common events that start the fire. Once the furniture is burning, the growth rate of the fire may be such that people are not given sufficient time to escape. Consequently, the draft furniture directive includes requirements for ignition resistance of up holstered furniture, the so-called first essential requirement, as well as require ments for safe escape time from the burn room once the item is on fire, the socalled second essential requirement. 2


Ignition of Upholstered Furniture The first essential requirement of the furniture directive deals solely with ignition resistance. Four levels are defined: Ignition by cigarette, by matchflame, by 20 g of newspaper and by 100 g of newspaper. The cigarette and the match flame are intended for furniture in domestic use and the newspaper for public and high risk premises. CEN, the European Committee for Standardization, is producing European standards for this purpose, under the general designation of EN or "European norms". CEN has so far met the task of producing standards for ignition resistance of upholstered furniture and mattresses against cigarette and match-likeflame.The tests for upholstered furniture, EN 1021-1 and EN 1021-2 have already been accepted. A cigarette or a small gasflameis placed in a model sofa that is made of the test material. The occurrence of ignition is studied. The tests are very similar to the corresponding ISO standards with one important exception. The match flame test, 1021-2, is milder than the ISO version. The ignition flame exposure is only 15 s compared to 20 s in ISO. The tests for mattresses, EN 597-1 and EN 597-2 are about to be accepted. However, tests for simulation of news paper sources have not advanced as far. In this case technical development work is required, so called prenormative research. The Commission has sponsored a programme of work directed towards standards development. Eight laboratories are working together. The approach is to simulate the heat impact on upholstery when exposed to a fire from 20 g of newspaper and 100 g of newspaper, respectively. A square gas burner of a similar shape as the California TB 133 burner was chosen. However, the geometrical dimensions are smaller than the TB 133 burner; roughly half the size. At present no standardization work for the first essential requirement has started at CEN on these tests since the prenormative research is not yet finished. SP is not involved in the work with the first essential requirement but we have nevertheless made some measurements of Heat Release Rate, HRR, from burning newspaper. Figure 1 shows data of HRR from different configurations of newspaper. The paper was put on slabs of mineral wool in a furniture mock-up. The mineral wool had thermal properties similar to the padding in upholstered furni ture. The HRR data do not tell us which fraction of the heat was received by the furniture which would be a direct measure of ignition capacity. However, the geometrical configuration of the chair is very similar and therefore the size and duration (= HRR curve) of the source would give us a very good indication of the ignition capacity. The different configurations gave different packing densities of the paper. Therefore the 100 g results give differences in peak HRR although the total energy release is the same as seen below in Table I. The 20 g newspaper consisted only of two sheets and therefore no difference occured. Paper size was 28 cm χ 38.5 cm.

Nelson; Fire and Polymers II ACS Symposium Series; American Chemical Society: Washington, DC, 1995.

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Testing Upholstered Furniture in Europe: CBUF

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Table I. Summary Data on Experiments with Burning Newspaper


100 g paper 100 g paper pile ball

20 g paper pile

20 g paper ball

42

19

6.6

6.7

1688

1720

301

356

14

12

2.4

2.7

lOOggile - - lOOgball 20 g pile 20 i §all

2 Time [min]

Figure 1 HRR measured on different configurations of newspaper. Sheets of paper were individually crumpled and laid up in a pile. Alternatively, a ball was formed where all sheets were crumpled together.

The TB 133 burner is designed to model the burning of 100 g of newspaper (when burning in a cage construction). The TB 133 burner, 20 kW for 80 s and THR 1600 kJ, is close to the 100 g paper data in the above experiments, although the HRR varies with paper configuration. This limited investigation (on HRR only) supports the TB 133 choice and the conclusions drawn by Ohlemiller and Villa . They carried out a comprehensive investigation including testing a series of chairs and taking heat flux measurements on the samples, which are directly related to ignition propensity. 3


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Combustion Behaviour of Upholstered Furniture-the CBUF programme The second essential requirement in the draft directive states that "the atmosphere

Room Scenario Full sized furniture


iï

Room Fire Model

in the room in which the upholstered furniture or related article are on fire should, despite the production of heat and smoke , remain for a reasonable period of time after ignition such that it does not endanger the lives or physical well being of exposed persons. This will be achieved by controlling the rates of heat release, smoke and toxic gas production. "

A very large prenormative research programme has been funded by the Commission with the objective of Furniture providing scientific and technical support for the functional requirements given in Calorimeter the second essential requirement. This Full sized furniture research programme is called CBUF; Combustion Behaviour of Upholstered Furniture. CBUF applies to domestic, ii public and high risk occupancies. Furniture Fire The CBUF-project started in 1993 and will last for two years. The total Model project budget is approximately 2.8 million dollars. Internationally well known and very experienced scientists are working together. Fire researchers, Cone Calorimeter testing experts and industry experts from 11 organisations participate. They come Composites from Sweden, UK, Italy, Finland, Denmark, Belgium, Germany and France. ιi The project manager is from DBI, Denmark. The technical co-ordination is Composite done by SP who also has the largest part Model in the project. Relationships will be developed y between (1) the conditions occurring in a full scale room scenario (ISO 9705 and Cone Calorimeter larger rooms) due to the burning of a piece of furniture, and (2) the results of Component materials bench scale tests on composites consisting of various layers of fabric, interliner and padding used in the construction of the furniture. These rela tionships will be based on room fire models and furniture fire models insofar as possible. Rate of heat release, smoke and toxic gas production will be the main fire parameters considered. r


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613

4

The furniture calorimeter (NT FIRE 032) and the cone calorimeter (ISO 5660) are the tests used. Relationships will be developed between test data from the cone calorimeter on composites and the large scale burning behaviour on full sized furniture, as measured in the furniture calorimeter. An attempt will also be made to develop a model where data on component materials, i.e. fabric, interliner and padding, can be combined to predict the composite fire data as measured in the cone calorimeter. Functional requirements will be examined by conducting room fire tests on furniture. Measured room fire conditions will be interpreted by doing fire hazard analysis and identifying tenability limits and associated times. These data will then be compared with predictions based on (1) furniture calorimeter data and existing room fire models, and (2) cone calorimeter furniture fire models and correlations. Reliable test protocols have been developed and verified for the cone calori meter and for large scale testing as well as procedures for toxic gas measure ments. Hundreds of tests in small and large scale tests have been performed. To determine time to tenability limits some hazard analysis needs to be carried out on the room scenarios which have been decided. Therefore room fire experiments are required. Then calculations are done with a room model, CFAST , on various geometries and conditions. In that way the choice of tenabili ty limits and time can be validated.


5

6

The Furniture Calorimeter. Of particular importance are the test methods used in the CBUF-programme. They must be repeatable, reproducible, robust and yield relevant data for prediction of the burning behaviour. Let us examine some of their features. The furniture calorimeter NT FIRE 032, see Figure 2, as defined by NORDTEST was first published in 1987. It was backed up with testing work on real furniture . NT FIRE 032 was revised in 1991. The combustion gases from the product are extracted into a 3 m χ 3 m hood. In the exhaust duct, measurements of gas species concentration, gas flow rate and smoke optical density are performed. HRR is calculated according to the oxygen consumption technique. A new technique for measuring a large variety of toxic gas species has been introduced, the so called FTIR (Fourier Transform InfraRed). This instrument makes infrared measurements simultaneously over the whole spectrum. Of special interest for furniture are for example HCN and NO . Quite recently, NORDTEST published a standard, NT FIRE 047 for FTIR measurements in fire testing. It was preceded by work done at VTT in 1990 . The FTIR technique is very promising. The concentration of a gas is measur ed continuously during a fire test. When combined with the mass burning rate, yield data can be determined. Older techniques often gave only the time average and are time-consuming and not very suitable for routine work. However, the FTIR used in fire testing is still a very new technique and therefore much care needs to be exercised when using it. Smoke optical density is measured with a white light system having a detector with the same spectral responsivity as the human eye. The mass loss rate from the sample is measured simultaneously, therefore, yield data of smoke can also be determined. 7

x

8

9

The Furniture Calorimeter is reproducible. Prior to the CBUF-pro gramme commencement a round robin was performed on NT FIRE 032. Six European laboratories participated. Good results were obtained for chair configurations, see Figure 3.


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FIRE A N D P O L Y M E R S Π

Optical density (lamp / photocell) Gas analysis ( 0 , CO, CO2) 2

Volume flow Temp, and differential pressure


Exhaust gases

Exhaust hood Test specimen on weighing platform V777777.

Figure 2

The furniture calorimeter. A full size, piece of furniture is placed on a scale under a hood. The test specimen burns without any restriction of air supply. Rates of heat release, smoke production, gas species production and mass loss are measured continuously.

It is clear that the results are very similar for the different laboratories. The best results were obtained with chairs, probably because the fire build-up does not rely onflamespread as for example with a three seat sofa. The cone calorimeter test protocol. The cone calorimeter, see Figure 4, was chosen for small scale testing in the CBUF programme. Both the composite product combinations and the individual components, fabric and padding, separately, are tested. All of the fire parameters that are mea sured in the furniture calorimeter are also measured in the cone calorimeter under controlled and defined conditions. Therefore it is assumed that cone calorimeter data can be used for predictions of the full-sized furniture items. A main problem is the prediction of the effects of furniture design. Therefore, a special test series of custom made chairs of similar materials but with different designs is included in CBUF to provide the necessary experimental data. Much time has been devoted towards the development of a procedure for sample preparation which could give reliable test data. In addition a small video was produced that shows this procedure. The result is a very detailed description that has been verified in a comprehensive round robin. This work was done out side of CBUF by SP and is currently under publication . An example of the good agreement between laboratories is given in Figure 5. 10


SUNDSTROM


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Hood for combustion gases

Measurement of gas species (02, CO,C02)and smoke optical density

Conical heater Spark igniter

Load cell for measurement of mass loss rate Figure 4

The cone calorimeter. A special procedure for sample preparation of furniture materials has been developed and verified.


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2

HRR (kW m" ) 800 π

2

Flux level 35 kW m 1

1

Plots: Zero time = time of increasing HRR

700

Η

600


500

-Labi Lab 2 Lab 3 Lab 4 Lab 5 Lab 6 Labi

5 Time (min) Figure 5

Round robin results from the cone calorimeter on a furniture composite.

CBUF will soon be finalized. The CBUF project is continuing and once the prenormative research for the furniture directive is finalized, which will be in 1995, there will be a massive amount of new data and knowledge available to be used by fire engineers and regulators for the benefit of fire safety and harmoniza tion of requirements. References 1

Gravigny, L., "Draft European Directive on the Fire Behaviour of Upholstered Furniture", Flame Retardants '92., pp 238-242, Conference. Elsevier Science Publishers Ltd. ISBN 1-85166-758-x.

2

de Boer, J.A., "Fire and Furnishing in Building and Transport. Statistical data on the Existing Situation in Europe.", Fire and Furnishing in Buildings and Transport Conference proceedings, pp 1-14, 6-8 November 1990, Luxembourg.

3

Ohlemiller, T.J., Villa K., "Furniture Flammability: an Investigation of the California Bulletin 133 Test. Part II: Characterization of the Ignition Source and Comparable Gas Burner", NISTIR 4348. June 1990. USA.

4

"Upholstered Furniture: Burning Behaviour - Full Scale Test", NORDTEST method NT FIRE 032, Helsinki, 1991.



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International Standard-Fire Technology-Reaction to Fire-Part 1 :Rate of Heat Release from Building Products (Cone Calorimeter method). ISO 56601:1993(E). International Organisation for Standardisation, Geneva, 1993.

6

Peacock, R.D.,Forney,G.P., Reneke, P., Portier, R., Jones, W.W., "CFAST, The Consolidated Model of Fire Growth and Smoke Transport", National Institute of Standards and Technology Technical Note, NIST TN 1299, 1993.

7

Sundström, B., "Full-Scale Fire Testing of Upholstered Furniture and the use of Test Data", Reprinted from "New Technology to Reduce Fire Losses and Costs", Elsevier, SP Technical Report SP-RAPP 1986:47.

8

"Combustible products: Smoke Gas Concentrations, Continuous FTIR Analysis", NORDTEST Method NT FIRE 047, Helsinki, 1993.

9

Kallonen. R., "Smoke Gas Analysis by FTIR Method. Preliminary Investigation", Journal of FIRE SCIENCES, VOL. 8-September/October 1990.

1 0

Babrauskas, V., Wetterlund, I., "Fire Testing of Furniture in the Cone Calorimeter - The CBUF Test Protocol", SP REPORT 1994:32.

RECEIVED March 23,

1995


Fire and Polymers II - ACS Publications - American Chemical Society

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