PVC Cable Fire Toxicity using the Cone Calorimeter

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1 1 Please cite as: Al-Sayegh, W.A., Aljumaiah, O., Andrews, G.E. and Phylaktou, H.N. PVC Cable Fire Toxicity using the Cone Calorimeter Proceedings of the IAFSS, 1 th Asia-Oceania Symposium on Fire Science and Technology, 1 th AOSFST, October 5-7, 215 in Tsukuba, Japan. Al-Sayegh, W.A., Aljumaiah, O., Andrews, G.E. and Phylaktou, H.N. Abstract Electrical cables with PVC sheaths were investigated for their ignition characteristics, heat release and toxic yields using the cone calorimeter. 4 KW/m 2 was required to get a significant heat release for PVC. A heated Temet Gasmet FTIR was used for the toxic gas analysis. Gas samples were taken from the cone calorimeter diluted exhaust duct and transferred to the FTIR using a 19 o C heated sample line, heated pump and filter and a second 19 o C heated sample line between the pump and the FTIR. The FTIR measurement zone was also heated at 19 o C so that no loss of HCl and other condensable gases occurred. This heated sample system enabled the theoretical HCl yield, based on the chlorine content of PVC, to be measured. This indicated that there were no other significant chlorine products in the well ventilated fires. A peak yield of.45 for HCl was found. There were significant yields of the irritant gas acrolein and formaldehyde and acrolein was the most important toxic gas. The PVC sample and the char that remained after the test were analysed using TGA and the results showed that only 41.6% of the chlorine in the sample was lost as HCl in the cone calorimeter test, the rest remained in the char. Keywords PVC Cable Fires, Toxic Gases, HCl, Acrolein, Cone Calorimeter. 1 Introduction The majority of deaths in fires (66%) are due to the effects of toxic gases rather than flames [1]. PVC is the second largest contribution after wood to fires in non-domestic premises [2] and its use in electrical cable insulation is one of the main sources of PVC in fires. It has been estimated that there are 25m of electrical cable per house (5m per room) and 14 fires/million km cable/year [3]. Electrical cable fires may occur as part of a fire load for a fire that has started elsewhere and spread to ignite the cables externally. This is simulated in the present work using the cone calorimeter to represent radiant heating from a fire that engulfs the cables. Cable fires may also start through an electrical fault that results in overheating of the cable and ignition of the sheaf. Such fires are more dangerous in that electrical cables tend not to be in view and often in air starved service ducts. Thus, the fire can spread unnoticed Energy Research Institute, University of Leeds, Leeds, LS2 9JT, UK address: profgeandrews@hotmail.com. until it ignites other material or the electric supply to the building fails as a consequence. Sundstrom [4] has reviewed methods of testing of cables for their fire resistance and concluded that current tests concentrate on fire propagation rates and not on toxicity. However, he concludes that the future must address the toxicity issue and the measurement requirements, as reliable test methods are lacking. Hirschler [5, 6] has compared the large scale cable tray fire tests of ASTM D921 and IEC with the cone calorimeter and concluded that the HRR and smoke production measured in the cone calorimeter can be used to predict the results of the larger scale tests. This was the reason for the use of the cone calorimeter in the present work, which used heated FTIR analysis for full acidic and irritant toxic gas production measurements for PVC cable sheaths. Lukas [7] showed that the series of cylinders that resulted from electrical cables in the 1mm by 1mm cone calo- The 1th Asia-Oceania Symposium on Fire Science and Technology,

2 2 Al-Sayegh et al. rimeter test section did not results in any significant (>1%) variation in the surface heat flux. Van Hees et al [8] investigated the cone calorimeter for electrical cable fire investigations and specifically looked at the effect of loss of pyrolysis products through the cut end of the cables. They showed that that there was little effect of the cut ends of the cables on time to ignition for all the cable sizes and compositions tested. Also there was no influence of the cut end on the heat release rate. The insertion of the cables into the depth of the specimen holder so that there was a metal wall seal to the end of the cable was shown to give more repeatable results [8], especially at low heat flux, and this Table 1. HCl and CO yields for PVC fires. Author Ref. Method CO Yield g/g Theoretical PVC C 2 H 3 Cl Babrauskas 9 NBS Cup Furnace.9.11 Babrauskas 9 SwRI/NIST.86.9 Babrauskas 9 Cone Calorimeter 35, 5, 75 kw/m 2 Babrauskas 9 Real Scale Fires PVC board 2 Large scale fire Bowes 1 Pyrolysis of 1kg of rigid PVC in 1m 3 furnace Blomqvist 11 Vertical cable fire test with FTIR Hull et al. 12 ISO Purser Furnace FTIR Hull et al. 13 Purser Furnace This work Cone Calorimeter + FTIR, PVC cables HCl Yield g/g % Max Yield HCL Persson and Simonson configuration for testing electrical cables was used in the present work. They concluded that the most repeatable test procedure with the cone calorimeter was to use the 1mm long electrical cables side by side in the 1mm wide test tray and this was used in the present work. This work was only concerned with electrical cable fire heat release rate and smoke production and undertook no testing on other fire toxic products. It is the aim of the present work to show that these cone calorimeter electrical cable test procedures can be used to determine the toxic gas yields. 2 Previous Work on Toxic Yields from Electric Cable Fires Several investigators have measured toxic yields in PVC fires. These are summarised in Table 1, which also gives the measurement method and identifies which were cable fires. The present results are included for comparison plus for HCl the theoretical yield, assuming that all the chlorine is emitted as HCl from the fire. The HCl yields are also given in Table 1 as a % of the theoretical yield and this shows that in most experimental fires, less than half of the chlorine in PVC is released as HCl, implying either measurement problems or that much of the original chlorine remains in the char. The key measurement problem is the loss of HCl by solution in water condensed from the fire product gases. Fully heated sampling systems are required for on line measurement, as used in the present work. There is no evidence of other significant chlorine products from PVC fires [1]. The present yields are much closer to the theoretical possibly due to use of heated FTIR analysis with no sample line losses of HCl. Table 1 also shows the CO yields and there was little correlation between these and the HCl yields. Purser [14] showed that in most fires the main toxic products are CO, HCN and irritant or acidic gases and the amounts depend on the thermal decomposition of the fire load, which depends on the temperature and oxygen supply. Although irritant and acidic gases are often quoted as being present in fires, from the reaction of those affected, there are very few measurements of these gases. The present work uses calibrated heated Fourier Transfer Infra-Red Spectroscopy (FTIR) specifically to investigate these irritant and acidic gases. The authors [15-2] have used heated FTIR for toxic gas analysis in small scale enclosed fires in a 1.6 m 3 fire facility with air starved fires for various fire loads. These results showed that the overall fire toxicity was dominated by relatively few species: CO, NO 2, SO 2, HCN, HCl, benzene, formaldehyde and acrolein. Other species contributed in total <1% of total toxicity in most fires. The ability of the heated FTIR technique to measure

3 all these species and others simultaneously in a fire makes it the ideal instrument for fire toxic gas analysis. 3 Experimental Methods Samples of PVC sheathed electric cables were burned on the cone calorimeter under the standard free ventilation conditions. Three different heat fluxes (2, 3 and 4 kw/m 2 ) were investigated so that the ignition heat flux could be determined. Strips of electrical cable 1cm long were placed side by side until the whole of the cone calorimeter square test section was full with one layer deep of electrical cable. The copper core was retained in the wires as they may contribute to the temperature rise, as a thermal heat sink. A heated Temet FTIR (Gasmet) was used for the toxic gas analysis. The FTIR had a multi-pass cell with gold-coated mirrors with a 2m path length and volume of.22l. This had an 8 cm -1 wavelength resolution and a cm -1 scanning range. This low resolution was used as this has a much better signal to noise ratio for complex multicomponent gas analysis. A liquid nitrogen cooled MCT detector was used that scans 1 spectra per second and several scans are used to produce a time-averaged spectrum. The Temet FTIR has an accuracy of 2% and a precision that is.1% of the measurement range. The Gasmet CR2 FTIR used in the present work was calibrated for 63 gases at variable concentrations totalling 411 calibration curves available to be used for qualitative or quantitative analysis. This calibration included all the significant species that are present in the gas sample from fires. The calibration wavelengths used for the key toxic species quantified in this work are shown in Table 2, together with the number of calibration points and the calibrated range. The only calibration necessary prior to the test was to zero the instrument on nitrogen. The calibration was checked for some gases, CO, CO 2, benzene and methane using certified span gases and the agreement was satisfactory [21]. The calibration was fitted with a best fit curve and could be extrapolated outside the calibration range. This was demonstrated using a Dekati 1/1 exact diluter. Samples were taken from the cone calorimeter diluted air exhaust duct and transferred to the FTIR using a 19 o C heated sample line, heated pump and filter and a second 19 o C heated sample line between the pump and the FTIR. The FTIR measurement zone was also heated at 19 o C so that no loss of HCl and other condensable gases occurred. There are two reasons to use completely heated sampling and analysis systems when sampling directly from fire product gases: loss of condensable species, mainly hydrocarbons and aldehydes and loss of species by solution in the water that condenses in unheated systems. The PVC cable sheath and its fire residues were analysed by thermal gravimetric analysis (TGA). A sample weight of about 5 mg was used and the weight resolution was 1 μg. The sample was heated in nitrogen to release volatile components and at higher temperatures to pyrolyse the PVC, followed by combustion in air to burn the remaining carbon in the char. The sample was heated at 2 o C per minute until a temperature of 1 o C was achieved. The temperature was kept at 1 o C for five minutes which allowed the sample to dry out and any water content to be determined. The sample was then heated to 55 o C at a rate of 2 o C per minute for 1 minutes this allows the volatile components to evaporate or pyrolyse but not to combust as no oxygen is present, this determines the HCl released as this is the only volatile product for PVC. Finally the air combustion phase was introduced where the sample was heated to 56 o C at a rate of 1 C per minute. The weight loss determines the carbon proportion of the sample, as any hydrocarbons, HCl or hydrogen would have been devolatilised by 55 o C. The PVC electrical cable covering had a thickness of 2.9mm. The cable was intended for use with voltages between 3 and 5 volts. The calorific value for PVC is 19.9 MJ/Kg. The elemental composition of the PVC coating was analysed and was very close to that for pure PVC. It had an H/C ratio of 1.53 compared with 1.5 for pure PVC and the Chlorine content was 55.3% compared with 56.8% for pure PVC. Table 2 FTIR Calibration data for key toxic species. Species No of cal. points Calibration range [ppm] Wave number range, cm -1 CO HCl CH 2 O Acrolein C 3 H 4 O Formaldehyde TGA Analysis of PVC Cable Sheath Fig. 1 shows the normalised value of weight loss versus temperature when heating PVC electrical cable sheaths in nitrogen (pyrolysis) and with air (combustion). Also shown in Fig.1 is the equivalent result for the residue that was left after the cone calorimeter PVC fire burnt to completion. The weight loss when heating the sample in nitrogen was 3

4 weight / original weight (mg/mg) mass/(original mass) (mg/mg) HRR(Kw/m2) 4 Al-Sayegh et al. due to the release of HCl, this occurs between 25 and 3 o C and is identical for heating in nitrogen and air. The elemental analysis gave 55% of the PVC mass as chlorine; this would produce a yield of HCl of 58% as shown in Table 1. Fig. 1 shows there was a 42% weight loss due to HCl loss in air and nitrogen. However, there is evidence of another volatile loss at 4-5 o C and assuming that this is also HCl the total weight loss due to release of HCl is 52% close to the expected total yield of HCl. Bowes [1] commented that 7% of the expected HCl yield (41%) occurs rapidly at 272 o C and this was found, as shown in Fig. 1. After 5 o C there was a small weight loss due combustion of hydrocarbons. At around 7-75 o C both pyrolysis and combustion show a further weight loss indicating further pyrolysis after most of the HCl was released. After 8 o C there was no further weight loss for heating in nitrogen or in air and this indicates that there is about 3% of residual char that does not burn. This will be shown later to be a feature of the cone calorimeter results Normalised values for TGA of PVC electrical Cable Temperature ( o C) Fig. 1. TGA mass loss as a function of temperature for PVC cable sheath, heating in N 2 for pyrolysis and in air for combustion Normalised Value for TGA of PVC Residue Temperature ( o C) Combustion Pyrolysis Pyrolysis Combustion Fig. 2 TGA mass loss as a function of temperature for PVC cable sheath debris after the fire, heating in N 2 for pyrolysis and in air for combustion. The char remaining after the cone calorimeter tests was also tested using TGA in the same way as for the raw PVC. The TGA results are shown in Fig. 2. This shows that the char still had a volatile component that was released in nitrogen and in air between 1 and 25 o C and at a lower temperature under pyrolysis conditions. All of this weight loss was at a lower temperature than in Fig. 1 and hence cannot be mainly HCl. These volatile components are probably hydrocarbons absorbed in the char after the end of combustion on the cone. The char was resistant to further weight loss from 25-5 o C and then there was a slow weight loss to 8 o C. It is possible that some of the HCl that is not released until after 4 o C in Fig. 1 remains in the char after the cone calorimeter test and is then released in the char TGA, as in Fig Heat Release Rate at Varying Heat Fluxes for a PVC Sample Time(s) 2Kw/m2 3Kw/m2 4 KW/m2 Fig. 3 HRR by oxygen consumption for PVC cable fires. 5 Mass Loss and Heat Release Rate The PVC sheathed cables with copper core inside were tested on the cone calorimeter and the HRR by oxygen consumption are shown in Fig. 3. This shows that 4 kw/m 2 was required to get a significant HRR for PVC. The toxicity measurements were carried out at 4 kw/m 2 where there was flaming combustion of the cables. Fig. 3 shows that the HRR peaked at 17 kw/m 2 for PVC. Van Hees et al. [8] have reported heat release data for 5 kw/m 2 incident radiant flux, for a range of unspecified sheathed electrical cables on the cone calorimeter. The range of HRR was from 15 7 kw/m 2. Some of the cables tested had a double peak in the HRR as a function of time, one at 1s and one at 4s after exposure to the radiation, but this was mainly for cables with the higher HRR. They had some results similar to the present work with a single peak at about 15 kw/m 2 after about 1s and these were probably PVC sheathed cables. The toxic gases for PP will be shown later to mainly occur during the short HRR period. Van Hees et al. [8] also found that the smoke emissions on the cone calorimeter tests had a similar profile to the HRR, with peaks in smoke when there was a peak in HRR. In the present work there were two phases of toxic release with most species such as HCl being released at the maximum HRR period and some toxic hydrocarbons such as 1,3 butadiene released later in

5 Yield Yield Yield (g/g) Yield g/g of CO Fig. 4 PVC yields g/g of toxic gases for 4 kw/m 2. 5 the burning period, as shown in Fig. 4. The large production of HCl from the PVC cable fires, as shown below and in Table 1, makes PVC a significant contributor to fire toxic risk Time(s) Yields of HCl at Varying Heat Fluxes Yield for Acrolein in 4 Kw/m2 fire Yield g/g of 1,3 Butadiene 2 Kw/m2 3 Kw/m2 4 Kw/m Time(s) Yield for formaldehyde in 4 Kw/m2 fire Toxic Yields Toxic yields (g/g) for some of the most important toxic species for PVC are shown in Fig.4. Yield data can be incorporated into fire models and there is a scarcity of yield data for species other than CO and smoke. The yields of HCl with PVC were sensitive to the radiant heat, but were in the.2 to.5 range. Table 1 shows that these yields are comparable with those reported by others for both large and small scale equipment. They are higher than most previous work has found, especially in small scale tests such as the Purser furnace test [12, 13]. However, the agreement was very good with the previous cone calorimeter work of Babrauskas et al. [9] for PVC sheet samples. It is considered that sample system losses of HCl probably play a significant role in some previous work. The present HCl yields are significantly lower than the 1% conversion of chlorine to HCl yield of.58. This may be due to incomplete conversion of the chlorine in the fire. The cone calorimeter debris was tested by TGA, as discussed above. There was a low temperature volatile gas loss, but at a lower temperature than was found for the fresh PVC. However, it was possible that the second stage HCl loss that occurred at higher temperatures in the TGA was the source of the Chlorine that was not released in the cone calorimeter tests. This was about 3% of the total Chlorine and if this was the case then the measured yield of HCl would be close to achieving a chlorine balance. Although the yields of formaldehyde and acrolein are low relative to other species, their high toxicity makes these very significant. There have been very few previously reported measurements of these yields and the very high emissions of acrolein with PVC electrical cable fires is a significant fire toxicity hazard. All the key toxic species occur at the time of peak heat release, as can be seen by comparing Fig. 4 with Fig. 3 for 4 kw/m 2. The present TGA results show that for PVC 7% of the HCl loss will occur early in a fire at temperatures of about 2-25 o C. 3% of the HCl is lost in a later higher temperature phase. In the cone calorimeter fires this results in an early release of HCl for PVC followed by a long duration continual release at a lower rate in the later stages of the fire, as shown in Fig. 4.. After the initial HCl release there is a release of formaldehyde. This is followed by a large release of acrolein in the PVC cable fire. For the PVC fire the results in Fig. 5 show a continuous release of hydrocarbons throughout the later stages of the fire and some of these are toxic. including 1, 3 butadiene which is shown

6 6 Al-Sayegh et al. in Fig. 4 to be generated in the later stages of the cable burning. C1 Total HC, ppm Time, s Fig. 5 C1 equivalent total hydrocarbons as a function of time for 4 kw/m 2 heat flux. The total C1 equivalent unburnt hydrocarbons are shown in Fig. 5. This was determined by converting each hydrocarbon measured by the FTIR to a C1 equivalent (x3 for propane for example) and then summating them. Comparison with the HRR results in Fig. 3 shows that total unburnt hydrocarbons peak at the time of the peak HRR. The total hydrocarbons were dominated by propane, methane and acetylene in order of their relative magnitude. Comparison with the CO yield results in Fig. 4 also shows a similar profile and this indicates an inefficient combustion source of the HC and CO, as there is amply excess air and so the equilibrium CO would be low. 7 Relative Toxicity Toxic gases are usually assessed in terms of threat to life using the using the LC 5 threshold toxic gas levels [22]. For impairment of escape the EU COSHH 15 minute levels [23] can be used [15-2], which are similar to the US AEGL-2 1 minute exposure limits [24] in terms of their purpose (to prevent impairment of escape), the individual values are similar but different. The most important toxic gases are shown in Table 2 using both methods of assessment. The two methods differ in their relative assessment of toxicity with LC 5 always giving a low influence of acrolein and COSHH always gives this a high influence. By expressing the toxic levels as a ratio to that for CO, the relative toxicity for LC 5 and COSHH 15 min can be compared, as in Table 3. Only for HCN is the relative toxicity the same for both methods. This means that gases that kill are different from gases that impair escape i.e. the acidic irritant gases that impair escape do not cause death. In the present work the major difference in the relative toxicity for HCl is important. For HCl the COSHH 15 min toxicity data indicate severe impairment of escape, but the LC 5 data indicate a low risk of death. However, impairment of escape due to the irritancy of HCl will lead to deaths in a fire, that are then ascribed to CO, as the delay in escape results in inhalation of high levels of CO. For mixed toxic gases in fires and in workplace exposure, the total toxicity is determined by first expressing the measured toxic gas concentrations as a ratio to the LC 5 or COSHH 15 min limits, n species, and then summating n to give a total N. If N LC5 is greater than 1 then death is likely and if N COSHH15min is greater than 1 then impairment of escape is likely. [23]. This procedure has been applied in the present work for the diluted products of the PVC fires. The individual toxicity n for a species as a ratio to the total N gives the contribution of that species to the overall toxicity. Table 3. Toxic gas critical levels and these relative to CO. Toxic Gas 15 Min Exposure Limit COSHH [23] LC 5 3 min [22, 24] COSHH Ratio to CO limit LC 5 Ratio to CO limit Carbon Monoxide Nitrogen Dioxide Hydrogen Cyanide CO 2 3, 1 1 NO HCN Benzene C 6H Formaldehyde CH 2O Acrolein C 3H 5O Formic Acid CH 2O SO2 SO HCl HCl 5 3,7 4.8 Table 3 shows major differences in the relative toxicity of acrolein and formaldehyde, which are important in the present work. This shows that acidic and irritant gases that may impede escape are not the most important in deaths in fires. Aljumaiah et al. [18-2] have shown for various materials in restricted ventilation compartment fires that LC 5 and COSHH 15 total N values have a similar variation with time in a fire with the peak fire toxicity always located by both methods at the same time in the fire. In the present work both LC 5 and COSHH 15 relative toxicities are presented. The total COSHH 15 and LC 5 total relative toxicity N values are shown in Figs. 6 and 7 respectively for PVC

7 COSHH (N) N LC5 cone calorimeter firest. For the LC 5 toxicity the N values were much lower but occurred at the same time as for COSHH 15. The total toxicity N COSHH15min was sensitive to the heat flux as this changes the pyrolysis temperature in the fire zone. The air dilution of the fire products in the freely ventilated test conditions of the cone calorimeter makes the concentration of the toxic species much lower than have been measured from enclosed compartment fires using the same FTIR [15-2]. CO levels were very low and CO was not a major contributor to the toxicity, as shown in Fig. 8. Both Figs. 6 and 7 show for 4 kw/m 2 heat flux a double peak in the total normalised toxicity graphs, this also occurs in all the toxic species yield results in in Fig. 4 and the total HC results in Fig. 5. Both peaks occur at the time of peak HRR in Fig. 3. The HRR rises rapidly at 1s and this is the first peak in the toxicity results. The HRR remains high and slowly increases to the maximum HRR at about 2s. Fig. 6 shows that the total toxicity is the same at both peaks. However, Figs 4 and.8 show for individual toxic species that HCl, CO and formaldehyde are highest at the first peak at 1s and acrolein is highest at the second peak Total N (LC5) vs.time Fig. 7 N LC5 as a function of time for 4 kw/m 2 heat flux Ratio of HCL concentration to COSSH Value Ratio 7 Comparing Total COSHH N for Varying Heat Flux kw/m 2 2 Kw/m2 3 Kw/m2 4 Kw/m Fig. 6 Total relative toxicity N for COSHH 15 min. for three incident heat fluxes Measured / COSHH 15 min. formaldehyde Time, s Fig. 8 Toxic species normalised to COSHH 15 min v time for 4 kw/m 2 for HCl, CO, acrolein and formaldehyde.

8 8 Al-Sayegh et al. Fig. 8 shows the main toxic species concentration normalised to the COSHH 15 min impairment of scape limits. This shows that CO is not a significant toxic gas. At the first toxic gas peaks the total toxicity is 53% from acrolein, 33% from HCl and 12% from formaldehyde and at the second toxic gas peak it is 64% from acrolein, 27% from HCl and 8% from formaldehyde. This is the first time that the importance of acrolein in the fire toxicity from PVC cable sheath fires has been reported. If the data for normalised LC 5 was used then the total N in Fig. 7 has the first peak 58% from formaldehyde, 37% from Acrolein and 21% from HCl. The second peak is 41% from Acrolein, 33% from formaldehyde and 2% from HCl. Both toxicity assessments show that CO is not important and that the irritant gases acrolein and formaldehyde dominate the toxicity and HCl was significant but only the third most important toxic gas. These results are for freely ventilated fires and CO will become more important in ventilation control fires with rich overall equivalence ratios. 8 Conclusions The cone calorimeter with freely ventilated fires is a good method for the evaluation of toxicity from materials as well as their HRR in freely ventilated fires. A heated sample system and FTIR is essential for work on toxic gases as the losses if water condenses in the sample system will remove many of the important toxic species. A comparison of toxic emissions for cable sheath materials of PVC showed that the dominant toxic gas was acrolein for both COSHH 15 min impairment of escape and LC 5 death criteria. HCl was a significant toxic species but not as important as acrolein and for LC 5 formaldehyde was more important than HCl, but for COSHH 15 min toxicity HCl was the second most important toxic gas. The important role of the irritant gases acrolein and formaldehyde in PVC cable fires has not previously been reported. Further work is required to confirm these results and to understand the pyrolysis kinetics and to ensure that similar conclusions are valid for under ventilated fires. Acknowledgement We would like to thank ABB and Tyco Electronics for the donation of production electrical cables for this work and John Staggs for arranging this link. We would like to thank the UK EPSRC for the LANTERN JIF award that provided the FTIR and associated hot gas handling equipment that was used in this work. Wadie A. Al-Sayegh would like to thank Saudi Aramco for a scholarship under which this research project was undertaken. References [1] HMSO, 212, UK Fire Statistics. [2] Persson, B. and Simonson, M., Fire Emissions into the Atmosphere, Fire Technology, 34: 3. [3] Andersson, P., Simonson, M. and Stripple, H., 23. Fire Safety of Up holstered Furniture, SP Swedish National Testing and Re search Institute SP Report 23:22. [4] Sundstrom, B., 26. Flammability Tests for Cables. 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9 Compartment Fire Heat Release and Toxic Gas Yields. Fire Safety Science, Vol. 1, pp [21] Daham, B.K., Andrews, G.E., Li, H., Ballesteros, R., Bell, M.C., Tate, J.E. and Ropkins, K. 25. Application of a portable FTIR for measuring on-road emissions, 2 pp. SAE Paper In Emissions Measurement and Testing 25 SAE SP-1941, p , ISBN [22] Fire Science and Technology Inc., Toxicity of fire gases, [23] Health and Safety Executive, 22. Control of Substances Hazardous to Health Regulations, HSE Books. [24] Stec, A.A. and T.R. Hull, eds. 21. Fire Toxicity, Woodhead Publishing Ltd: Cambridge. 9