| Popis: |
The steady state tube furnace (Purser furnace, BS 7990 and ISO TS 19700) has been used in conjunction with FTIR gas analysis to investigate the toxic product yields of fire effluents. The repeatability and interlaboratory reproducibility of the apparatus is shown to be satisfactory, based on results from 6 operators at 4 laboratories. The set-up and calibration of FTIR for gases and volatiles is described, together with a discussion on reliability and interpretation of spectra. A novel recirculation system for calibration of volatile components (including organoirritants) has been validated by quantification in triplicate. Seven materials (LDPE, Nylon 6.6, Polystyrene, PVC, Medium density fibreboard with and without flame retardant and glass reinforced polyester) were investigated under different fire conditions, and the results presented in terms of toxic product yields and predicted fire gas toxicity as a function of equivalence ratio. This showed that in the case of PVC and nylon 6.6 the most toxicologically significant species were HCl and HCN respectively, in other materials, such as LDPE and polystyrene, CO was the major toxicant, and for the polyester, very high yields of CO were observed. Data from the Purser furnace and the NF X 70-100 toxicity test are compared for the seven materials, showing generally good agreement for all products except hydrocarbons. The clearer definition of fire condition from the Purser furnace allows better estimation of the fire condition of the NF X test. The yields of CO and hydrocarbons show good agreement with predictions based on data from the fire propagation apparatus (ASTM E2058), both methods using equivalence ratio to define the fire condition. Similar comparisons have been made with large scale test data from the ISO 9705 room again showing good agreement, and highlighting the ability of the tube furnace to identify the fire condition occurring in the large scale test. |
