Smoke toxicity and thermal hazards of fire resisting glass with high fire resistance rating

Abstract

Architectural features with glass panels have been designed in big modern construction projects. Fire resisting glass products have the ability to remain their integrity in fires. They are good replacements of standard glass products used in buildings. It has been observed that smoke is emitted when burning the protective layers of those glass products. The smoke emitted from these products can be potentially harmful during fires, causing injuries or even deaths. The objective of this thesis is firstly to carry out an in-depth study on smoke toxicity and other related fire safety aspects of fire resisting glass with higher rating. Secondly, thermal hazards upon breaking of glass in a room fire are also studied. Common types of fire-resisting glass available, especially the ones with high fire resistance rating, were reviewed. The compositions of fire resisting glass products are not released by manufacturers, especially those from the Far East. It has been observed that smoke is emitted when burning the protective layers of glass products. Relevant fire safety standards and codes were reviewed. Key aspects such as fire resistance, impact safety and toxic potency were studied. Smoke toxicity is an important aspect in fire safety assessment. The hazards of smoke and common smoke toxicants were reviewed. Selected methods used for quantifying fire gas toxicity such as lethal toxic potency and fractional effective dose were outlined. Applications of bench-scale and large-scale smoke toxicity tests were also discussed according to their fire effluent generating and assessing methods. Samples of insulating glass available in the local market were selected. Chemical compositions of the protective layers and gases discharged from the protective layers of fire resisting glasses upon heating in different atmosphere were examined. A variety of techniques, including X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), thermogravimetric Fourier transform infrared spectroscopy (TG-FTIR), pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) and tubular furnace coupled Fourier transform infrared spectroscopy (TF-FTIR), were employed. Cone calorimeter has been proven to be a suitable tool for assessing the smoke toxicity of materials under well-ventilated conditions. Five samples of fire-resisting glass were tested with a cone calorimeter to study their behaviour under different fire conditions. The toxic gas yields others than their concentrations measured were used for lethal toxic potency and fractional effective dose estimations. The calculation procedures were clarified. Destruction of window glass can introduce ventilation through the opening causing high heat release rate and even flashover. This brings concerns to the fire safety of buildings with large window area or even glass facade. Many useful correlation equations derived for estimating the heat release rate for a post-flashover room fire were applied in performance-based design. Three correlation equations were justified by reported experimental data. Two sets of reported experimental results on post-flashover room fires with transient heat release rates measured by oxygen consumption calorimetry were used.