Tuula Hakkarainen

Smoke gas analysis by Fourier transform infrared spectroscopy – summary of the SAFIR project results

The determination of toxic components from fire gases is difficult because the environment is hot, reactions are often temperature dependent, and a lot of soot may be produced. Due to the different properties of the gas components, a different timeconsuming procedure for each species has traditionally been used. The use of FTIR (Fourier Transform InfraRed) spectrometers as a continuous monitoring technique overcomes many of the problems in smoke gas analyses. FTIR offers an opportunity to set up a calibration and prediction method for each gas showing a characteristic spectral band in the infra-red region of the spectrum. The objective of this project was to further develop the FTIR gas analysis of smoke gases to be an applicable and reliable method for the determination of toxic components in combustion gases related to fire test conditions. The project included the following tasks: small scale and large scale sampling; analysis, calibration and software techniques; the verification of the method; and an interlaboratory trial. The optimum probe design, filter parameters and the most suitable sampling lines in terms of flow rate, diameter, construction material and operating temperature have been specified. The gas adsorption onto the filter and the soot have been measured. In the large scale, special concern was given to the probe design and the effects of the probe location in relation to the fire source as well as practical considerations of the sampling line length. Quantitative calibration and prediction methods have been constructed for different components present in smoke gases. Recommendations on how to deal with interferents, non-linearities and outliers have been provided and a verification method for the spectrometer for unexpected variations and for the different models have been described. FTIR measurement procedures in different fire test scenarios have been studied using the recommendations of this project for measurement techniques and analysis, and real precision values for specific test scenarios have been estimated. Also a proposal for draft standard of the FTIR method for smoke gas analysis has been prepared. An interlaboratory trial of the FTIR technique in smoke gas analysis was carried out to define the repeatability and reproducibility of the method in connection with a small scale fire test method, the cone calorimeter.

Post-Flashover Fires in Light and Heavy Timber Construction Compartments

A series of fire experiments was performed to study the gas temperature development and charring behaviour of timber construction compartments. The measured gas temperatures were 300-500 C lower than predicted by the parametric temperature-time curves of Eurocode 1 for unprotected and insufficiently protected timber structures. For structures protected with a double layer of gypsum plasterboard, the agreement was better. In all cases, however, the prediction was on the safe side. One protective layer of gypsum plasterboard delayed the onset of charring for 20 min. Using two layers, the delay time was doubled. Reduced charring rates for long exposure times were observed, resulting from the increasingly protective effect of the char layer withtime.

Rate of heat release and ignitability indices in predicting SBI test results

Rate of heat release and ignitability indices are applied to predict the European fire classification based on FIGRA values from Single Burning Item (SBI) tests for building products. Both indices can be calculated from cone calorimeter test results measured at 50 kW/m2. Within its validated range, the predictive procedure gives the correct classification for 90% of the products studied. The model provides a practical tool to support product development and quality control.

Cascading Failures: Dynamic Model for CIP Purposes - Case of Random Independent Failures Following Poisson Stochastic Process

Cascading failures are a challenging issue in Critical Infrastructure Protection (CIP) and related modelling, simulation and analysis (MS & A) activities. Critical Infrastructures (CIs) are complex systems of ever increasing complexity. A single failure may be propagated and amplified resulting in serious disruptions of some societal vital services. A dynamic model describing cascading random failures that occur following Poisson Stochastic Process (PSP) is proposed. The proposed model considers only independent failures. Additional R & D effort is necessary before extending the model to dependent failures.