Fire toxicity - The elephant in the room?

Fire toxicity is the largest cause of death and injury from unwanted fires, yet it is the least well studied area of fire science and engineering. Fire toxicity increases by factors up to 50, as the fire becomes under-ventilated. This has proved difficult, but not impossible, to replicate in a controlled way on a bench-scale. Clear correlations have been observed between the stoichiometric equivalence ratio, and the yields of the major asphyxiants, carbon monoxide and hydrogen cyanide. In addition, irritant components of fire effluents, which have an instantaneous effect, can incapacitate fire victims, trapping them in a fire. However, the longer term toxicants present in fire effluents, such as the carcinogenic polycyclic aromatic hydrocarbons, and the microscopic particulates which result from their agglomeration are probably responsible for hundreds or thousands more deaths than the acute asphyxiants and irritants

Assessment of the fire toxicity of building insulation materials

A significant element in the cost of a new building is devoted to fire safety. Energy efficiency drives the replacement of traditional building materials with lightweight insulation materials, which, if flammable can contribute to the fire load. Most fire deaths arise from inhalation of toxic gases. The fire toxicity of six insulation materials (glass wool, stone wool, expanded polystyrene foam, phenolic foam, polyurethane foam and polyisocyanurate foam) was investigated under a range of fire conditions. Two of the materials, stone wool and glass wool failed to ignite and gave consistently low yields of all of the toxic products. The toxicities of the effluents, showing the contribution of individual toxic components, are compared using the fractional effective dose (FED) model and LC50 (the mass required per unit volume to generate a lethal atmosphere under specified conditions). For polyisocyanurate and polyurethane foam this shows a significant contribution from hydrogen cyanide resulting in doubling of the overall toxicity, as the fire condition changes from well-ventilated to under-ventilated. These materials showed an order of increasing fire toxicity, from stone wool (least toxic), glass wool, polystyrene, phenolic, polyurethane to polyisocyanurate foam (most toxic)

The influence of carbon nanotubes on the combustion toxicity of PP/intumescent flame retardant composites

In recent years, carbon nanotubes (CNTs) have emerged as a promising candidate for improving the flame retardancy of polymer materials, as well as other physical properties. However, few researches have been focused on the influence of this nanoscale material on the combustion toxicity of polymer composites during combustion. In this work, the fire toxicity of polypropylene (PP) composites with intumescent flame retardants (IFRs) and CNTs has been investigated by a Purser Furnace apparatus, which is called steady state tube furnace (SSTF) and enables different fire stages to be created. The Thermo gravimetric analyzer (TGA) and derivative thermo gravimetric analysis (DTG) data indicate that the thermal stability of PP composites was increased by the addition of IFRs or CNTs. However, the SSTF results show that PP samples with IFR or CNTs or both, produced much more carbon monoxide (CO) compared to neat PP during all fire stages, resulting in a much lower CO2/CO ratio. Furthermore, an interesting finding is that the effect of CNTs on the smoke production and CxHy yield of the PP samples during the combustion changes with the combustion equivalence ratio. It indicates that the presence of CNTs promote the formation of smoke particulates from hydrocarbon, but this effect only exist when oxygen supply is not adequate. It is also concluded that the air ventilation and combustion temperature play significant roles in the fire effluent production of PP samples and the morphology of soot particulates

Analysis of fire deaths in Poland and influence of smoke toxicity

Dwelling fires have changed over the years because building contents and the materials used in then have changed. They all contribute to an ever-growing diversity of chemical species found in fires, many of them highly toxic. These arise largely from the changing nature of materials in interior finishes and furniture, with an increasing content of synthetic materials containing higher levels of nitrogen, halogen and phosphorus additives. While there is still a belief that carbon monoxide is the major lethal toxic agent in fires, the hydrogen cyanide and acid gases released from these additives are now well-recognised as major contributory causes of incapacitation, morbidity and mortality in domestic fires. Data for the total number of 263 fire death cases in the Mazowieckie region (mainly Warsaw area) of Poland between 2003-2011 for dwellings fires were obtained from pathologists, forensic toxicologists, fire fighters and analysed. Factors contributing to the death such as the findings of the full post mortem examination (age, sex, health status, burns), the toxicological analysis (carbon monoxide, alcohol etc.), and a thorough investigation of the scene (fire conditions, fuel, etc.) were taken into account and are summarised. [Abstract copyright: Copyright © 2017 Elsevier B.V. All rights reserved.

Enhanced mechanical, thermal and flame retardant properties by combining graphene nanosheets and metal hydroxide nanorods for Acrylonitrile–Butadiene–Styrene copolymer composite

Three metal hydroxide nanorods (MHR) with uniform diameters were synthesized, and then combined with graphene nanosheets (GNS) to prepare acrylonitrile–butadiene–styrene (ABS) copolymer composites. An excellent dispersion of exfoliated two-dimensional (2-D) GNS and 1-D MHR in the ABS matrix was achieved. The effects of combined GNS and MHR on the mechanical, thermal and flame retardant properties of the ABS composites were investigated. With the addition of 2 wt% GNS and 4 wt% Co(OH)2, the tensile strength, bending strength and storage modulus of the ABS composites were increased by 45.1%, 40.5% and 42.3% respectively. The ABS/GNS/Co(OH)2 ternary composite shows the lowest maximum weight loss rate and highest residue yield. Noticeable reduction in the flammability was achieved with the addition of GNS and Co(OH)2, due to the formation of more continuous and compact charred layers that retarded the mass and heat transfer between the flame and the polymer matrix

Stability of Isocyanates Sampled in Fire Smokes

Inhalation of airborne isocyanates is associated with acute asthma attacks and inflammation in the respiratory tract as well as cancer. These highly reactive compounds are used as monomers in various applications such as foams for insulation materials and upholstery furniture and are therefore commonly found in fire smoke from insulation materials, such as rigid polyisocyanurate (PIR) foams. Consequently, there is an increasing concern regarding the potential adverse health effects they may cause during this type of exposure. The aim of this study was to investigate the stability of generated isocyanates from aerobic pyrolysis of PIR after sampling in the derivatization solution as well as after sample preparation to establish the optimal storage conditions and rate of degradation. Both airborne and particle-bound isocyanates were collected, using dibutylamine as derivatization agent in a midget impinger and impregnated filter after the impinger. The rapid degradation of the generated isocyanates after sampling emphasizes the need for a prompt sample preparation and analysis, in particular for the collected mono-isocyanates, as the concentration decreased by 50% within 4–8 h

Numerical simulation of decomposition of Polymer Nano-composites: Investigation of the Influence of the Char Structure

In recent years, nano-particles such as nano-clays, carbon nanotubes and graphenes have been extensively used in flame-retardant polymeric materials. The surface char layer formed in combustion acts as protective barriers that limit the heat transfer into the unpyrolysed polymer and volatilization of combustible degradation products and diffusion of oxygen into the material. A numerical simulation tool Thermakin is used to simulate the thermal decomposition of the neat polymers (polypropylene (PP), Acrylonitrile Butadiene Styrene (ABS)) and corresponding nano-composites (PP/multi-walled carbon nanotube (PP/MWCNT) and ABS/ graphene nano-sheets /NiFe-layered double hydroxide hybrid (ABS/GNS-LDH) in cone calorimetry experiments. PP/MWCNT forms a porous network while ABS/GNS-LDH forms a compact, dense char layer during combustion. With appropriate input parameters, the heat release rates (or mass loss rates) are predicted very well. Finally, the effect of input parameters on model outputs are discussed

Numerical Simulation of Decomposition of Polymer Nano-composites: Investigation of the Influence of the Char Structure

AbstractIn recent years, nano-particles such as nano-clays, carbon nanotubes and graphenes have been extensively used in flame-retardant polymeric materials. The surface char layer formed in combustion acts as protective barriers that limit the heat transfer into the unpyrolysed polymer and volatilization of combustible degradation products and diffusion of oxygen into the material. A numerical simulation tool Thermakin is used to simulate the thermal decomposition of the neat polymers (polypropylene (PP), Acrylonitrile Butadiene Styrene (ABS)) and corresponding nano-composites (PP/multi-walled carbon nanotube (PP/MWCNT) and ABS/ graphene nano-sheets /NiFe-layered double hydroxide hybrid (ABS/GNS-LDH) in cone calorimetry experiments. PP/MWCNT forms a porous network while ABS/GNS-LDH forms a compact, dense char layer during combustion. With appropriate input parameters, the heat release rates (or mass loss rates) are predicted very well. Finally, the effect of input parameters on model outputs are discussed