Estimating Data for Incapacitation of People by Fire Smoke

Fire hazard and risk analyses establish the basis for providing conditions of safety for people, including those that are more sensitive to fire smoke than others. For this purpose, this paper develops a method for estimating, from information on lethal and incapacitating exposures for rats, smoke toxic potency values for incapacitation of smoke-sensitive people. For those engineering applications where the mix of combustibles is unknown, generic values are derived of the concentration of smoke that would incapacitate smoke-sensitive people in 5 min: 6 g/m³ for a well-ventilated fire and 3 g/m³ for an underventilated (e.g., post-flashover) fire. These values are estimated with significant assumptions in their derivation, resulting in an estimated uncertainty of about a factor of two. Further, there is a wide range of smoke toxic potency values reported for various combustibles, and some of these will lead to values significantly higher or lower than these generic figures.     

Occupational exposure to natural radiation

Natural sources of radiation can make an important contribution to the exposures of people at work. Two areas of ine interest are work with minerals having elevated concentrations of activity and work in buildings where radon daughter concentrations are elevated.The Euratom Directive on ionising radiation requires that the handling of radioactive substances be reported to national authorities. National authorities may waive this requirement where the activity per unit mass is below 100 Bq g^?1, or for solid natural radioactive substances, 500 Bq g^?1. An investigation was undertaken in five factories to determine whether work with minerals having levels of natural activity below these might lead to significant doses. Models based on the data collected were used to relate the activity in the minerals to the effective dose equivalent arising from gamma radiation, inhalation ohow that the activity, and intake of long-lived activity. These assessments show that the activity concentration at which exposures to airborne dust could lead to doses equal to one-tenth of the dose limit for workers are 0.3 Bq G^?1 for thorium-232 and 1 Bq g^?1 for uranium-238. Above these values, radiological supervision may be necessary.In a separate study, measurements of radon daughter concentrations were made in seventy workplaces. Concentrations in some premises approached or exceeded the derived air concentration for occupational exposure. The highest concentrations were found in premises with low ventilation rates.     

Fire Performance of Phase Change Material Enhanced Plasterboard

Sustainable construction materials are increasingly being used to reduce the carbon footprint of modern buildings. These materials have the potential to change the fire dynamics of compartments by altering the compartment energy balance however there is little quantitative understanding of how these materials behave in the event of a real fire. The changes in fire dynamics may be due to increased fuel load in a compartment, reduced time to failure or promotion of flame spread. The objective of this research is to quantify how Phase Change Materials (PCMs) perform in realistic fire scenarios. It was found that a plasterboard product containing microencapsulated PCMs will behave similarly to a charring solid and have the potential to contribute significant fuel to a compartment fire but that they maintain integrity for the duration of flaming period. The critical heat flux for this product was determined in the cone calorimeter to be 17.5 ± 2.5 kW m^?2, the peak heat release rate and mass loss rate ranged from 60.2 kW m^?2 to 107 kW m^?2 and 1.88 g s^?1 m^?2 to 8.47 g s^?1 m^?2 respectively for exposures between 20 kW m^?2 and 70 kW m^?2. Sample orientation was found to increase the peak heat release rate by up to 25%, whilst having little to no effect on the mass loss rate. These parameters, in addition to the in-depth temperature evolution and ignition properties, can be used as design criteria for balancing energy savings with quantified fire performance.     

Reliability based determination of material partial safety factors for cast iron beams in jack arched construction exposed to standard and natural fires

Cast iron beams were extensively used in many 19th century structures, especially in fireproof flooring systems (such as jack arch). Many such structures are still in use today and it is important that they fulfil the current requirements of fire resistance when there is a change of use. These structures are out of scope of modern design codes and old design codes do not provide guidance for fire resistance design. Furthermore, cast iron is a brittle material weak in tension, and there are many uncertainties in its mechanical properties at ambient and elevated temperatures due to material flaws. It is necessary to quantify the probability of structural failure and to introduce safety factors to reduce the probability of structural failure in fire to an acceptable level. This paper presents the results of a detailed study whose purpose is to derive appropriate safety factors to achieve different levels of reliability, for fire safety design of cast iron beams. In this study, a fibre analysis method has been used to calculate the moment capacity of four different types of cast iron cross section. Using randomized stress-strain-temperature relationships, based on variability of the different governing parameters (under tension: maximum stress, 0.2% proof stress, corresponding strains at maximum stress (strength) and failure; under compression: Young's modulus, proportional limit, 0.2% proof stress and the maximum stress), the probability distribution of moment capacity has been calculated. Based on the criterion of cast iron beam failure not exceeding probabilities of 10⁻¹, 10⁻² and 10⁻³, material safety factors of 1.5, 3.0 and 5.0 respectively have been obtained.     

A Quantitative Infrared Imaging System for In Situ Characterization of Composite Materials in Fire Tests

A novel non-intrusive measurement system based on quantitative infrared imaging has been designed and developed specifically for the study of composite plates submitted to fire. The system consists of two synchronized infrared cameras that image both sides of the sample during a fire test, providing surface temperature maps spatially corregistered. Flame effects on measured temperature are minimized through selection of a spectral band with near negligible infrared absorption-emission (wavelength centre 9585 nm, full width at half maximum 135 nm), as well as software post-processing. An ad hoc experiment has shown that this procedure retrieves surface temperatures with an uncertainty of \(\pm 5\) K, compared to a systematic error larger than 60 K for a classic thermographic measurement. Surface emissivities of both sides of the sample are measured and included in the retrieval procedure. By adding a flash lamp, the system implements an adaptation of the classical Parker’s flash method to thermally thick samples, providing also a map of thermal diffusivities along the sample both before and after the burning. In the region most degraded by fire, the effective thermal diffusivity is reduced approximately one order of magnitude as compared to the pre-test value (from 5.9 × 10^?7 m² s^?1 to 0.5 × 10^?7 m² s^?1). Several composite samples have been analysed while exposed to fire in different conditions, showing that thermal diffusivity after the burning shows a strong correlation with the local maximum temperature reached during the test. More precisely, in the temperature range between \(\sim \)325 and 350\(^{\circ }\)C a drastic change in diffusivity seems to takes place, in a way that suggest a phase change.     

Reliability-based load factors for airblast and structural reliability of reinforced concrete columns for protective structures

Reliability-based design allows the decision-maker to select the level of reliability for a specific explosive blast loading scenario. Important to this is an understanding of airblast and resistance uncertainty. Reliability-based load factors are calculated and are dependent on the variability of model error, explosive mass and range. Reliability-based design load factors (RBDFs) are estimated for explosive ordnance, terrorism, weaponeering and other scenarios. The effect of RBDFs on structural reliabilities for reinforced concrete (RC) columns is then calculated where resistance and loading are random variables, and compared to target values. It was found, for realistic combinations of range and explosive mass variabilities, that RC columns designed to existing standards have a significant margin of safety with a probability of failure of 1?×?10^?3 to 1?×?10^?5. However, if there is large airblast variability, then the application of RBDFs is necessary to ensure that safety levels are acceptable according to international standards.     

Development of a Risk Assessment Method for Life Safety in Case of Fire in Rail Tunnels

The present paper describes the development of a risk assessment methodology to quantify the life safety risk for people present in a rail tunnel in the context of the creation of a fire safety design. A bow-tie structure represents the risk assessment model, starting from major contributing factors leading to disastrous events. Using past accidents for the construction of the event tree part of the bow-tie, the most important factors are determined to be: human behaviour; fire growth; ventilation conditions; safety system (e.g. Smoke & Heat Exhaust, detection, voice communication, etc.); population density. These factors are incorporated into the event tree using pathway factors. Frequencies are calculated for each branch outcome based on data from research projects, fault tree analysis and engineering judgement. For the determination of the consequences, the method makes use of three integrated models: the smoke spread, the evacuation and the consequence model. The models can take into account all types of geometry and materials, human behaviour and different susceptibilities of people for smoke. Together, they determine the possible number of fatalities, by means of an FID (Fractional Incapacitation Dose) value, in case of a fire in a rail tunnel. The final risk is presented by the expected number of fatalities, the individual risk and the societal risk. The societal risk is demonstrated by means of an FN-curve (Frequency/Number of Casualty-curve).     

Determination of volatile organic compounds and associated health risk assessment in residential homes and hostels within an academic institute,New Delhi

The purpose of this study was to investigate the concentrations of volatile organic compounds (VOCs) in different indoor microenvironments of residential homes and hostels in an academic institute, in New Delhi, during March–May 2011. Eleven VOCs (aromatic and halogenated) were assessed. Sampling and analytical procedure were based on National Institute for Occupational Safety and Health (NIOSH) standard method. The lifetime cancer and non‐cancer risk were calculated for targeted VOCs using US Environmental Protection Agency guidelines. The mean concentrations of ∑ VOCs (sum of monitored VOCs) and individual VOC were found to be higher indoors as compared to outdoors at both types of premises. Indoor to outdoor (I/O) ratios of the targeted VOCs exceeded 1.0, suggesting the significant presence of indoor sources. Strong correlations between I/O concentrations of VOCs in the current study suggest the presence of common sources. Factor analysis (FA) was used for source evaluation separately at two premise types. The estimated lifetime cancer risks in the current study for all occupants at both premises exceeded 10^?6.     

Predicting the Fire Dynamics of Exposed Timber Surfaces in Compartments Using a Two-Zone Model

There is an increasing desire to use more engineered timber products in buildings, due to the perceived aesthetics of timber and desire for more sustainable architecture. However, there are concerns about fire performance of these products especially in taller buildings. This has led to renewed research to understand the behaviour of timber surfaces in compartments exposed to fire. This paper describes a two-zone calculation model for determining the fire environment within a compartment constructed from timber products where varying amounts of timber are exposed on the walls and ceiling. A set of eight full-scale compartment experiments previously reported in the literature are used to assess the capability of the model. The fire load energy density in the experiments ranged from 92 MJ/m² to 366 MJ/m² comprising either wood cribs or bedroom furniture with the largest compartment having dimensions 4.5?×?3.5?×?2.5 m high with an opening 1.069 m wide?×?2.0 m high. The experiments were ventilation-controlled. It is shown that the model can be used to provide conservative predictions of the fire temperatures for compartments with timber exposed on the walls and/or ceiling as part of an engineering analysis. There are several limitations that are discussed including the need to consider the debonding of layers in the case of cross-laminated timber. It is recommended that further benchmarking of the model be done for different ventilation conditions and with engineered timber products where debonding does not occur. This will test the model under a wider range of conditions than examined in this paper.     

A probability-based Monte Carlo life-risk analysis model for fire emergencies

The paper proposes a probability-based Monte Carlo life-risk analysis model for fire emergencies. Based on the hazardous conditions in each compartment of a building and the evacuation path of each occupant, the model calculates the probabilities of injury and death determined by fractional effective doses due to heat and toxic gases, considers the probability of death due to fire spread, and produces the probabilities of injury and death for each occupant. Then these probabilities for all occupants are summed to give the total probabilities of injury and death in a Monte Carlo run, and statistics about the total probabilities of all Monte Carlo runs are produced for each fire scenario. According to the statistics and scenario composition, the expected risks of injury and death in the building are calculated. The model is applied to a life risk analysis of 6- and 12-storey apartment buildings. The results show that for these buildings, injuries and deaths are mainly limited to the rooms of fire origin and the effects of building area and the number of storeys on life risk are slight. The predictions for different layouts are in good agreement with the numbers of injuries and deaths given by Canadian and US statistics.     

用于模拟建筑火灾的风险分析模型CUrisk的开发和火灾案例分析

加拿大卡尔顿大学开发了火灾风险计算机模型CUrisk，用以评估四层木结构商品建筑的火灾安全设计。该模型包括系统模型和许多子模型。系统模型用于设定风险分析框架及控制子模型数据流。它还负责计算每个火灾场景的生命危险值。其他子模型包括火灾增长、烟气运动、边界失效火灾蔓延、人员反应和疏散以及建筑造价和经济损失等模型。利用子模型的输出数据，系统模型可计算三个决策参数：对生命的预期风险、对受伤情况的预期风险以及消防成本预期。这些参数是以可能的火灾场景及相关概率为基础的。文章简要介绍了CUrisk模型，并介绍了运用该模型对四层商业建筑所进行的多火灾场景风险分析的结果。     

A probabilistic occupant response model for fire emergencies

The present paper describes a probabilistic occupant response model for fire emergencies, which is integrated into a fire risk analysis model called CUrisk. Based on the PIA process, i.e., Perception, Interpretation and Action, the occupant response model predicts the probabilities of occupants perceiving fire signals due to direct perception, receiving fire alarms due to the activation of local alarms, sprinklers, the central alarm and the voice alarm, being warned by the other occupants and fire department, and taking actions including pulling the fire alarm, warning other occupants, calling the fire department, and commencing evacuation. The occupant response model is applied to predict the probabilities of evacuation initiation for a number of scenarios that consider combinations of fire detection and alarm systems for a mid-rise building. The results of the model show that asleep occupants need much longer response time to start evacuating and have lower probabilities of starting evacuation than awake occupants, which are consistent with what is observed in reality. Additionally, fire protection systems with only local alarms and only sprinklers connected to the central alarm can be improved significantly with systems with smoke detectors alone or combined with sprinklers connected to a central alarm, which result in higher probabilities of evacuation initiation with shorter delay times.     

An empirical radon emanation model for residential premises

Based on an averaging technique, a methodology has been established to estimate an effective radon emanation factor M for residential premises. The model shows that the new term M and the ventilation rate are the essential parameters in estimating the level of indoor radon. M includes two components: the radon emanation rates of internal surface materials and the ratio of surface areas of applicable materials to premises volume. The value of M can be determined from on-site measurements. Different ventilation modes of a sampled residential unit during daytime and nighttime, with air conditioner on, window-open, and window-closed were included in site measurements. Each ventilation mode was measured twice during daytime and twice at night. During the investigation, air exchange rate, and indoor and outdoor radon levels were monitored simultaneously. The results of measurements were then used to verify the model. The value of M was found to be 31.7 Bq m⁻³ h⁻¹. The model is valid if the air exchange rate is larger than 0.2 h⁻¹.     

A Risk-Based Method of Deriving Design Fires for Evacuation Safety in Buildings

This article presents a risk-based method for building fire safety design. Because the design fire is the most critical aspect of a building fire safety design, this article uses reliability theory to derive design fires from the fire risk acceptance criteria. The fire scenarios are modeled by an event tree, where different fire protection systems are presented as pivotal events. The number of casualties is estimated by the occupant number and the probability that an untenable condition is reached before occupants evacuate to a safe location. Using the probability and consequence of each fire scenario, the expected risk to life is used to integrate the fire risk acceptance criteria into the determination of the target reliability index. A global optimization method is then applied to the reliability index to obtain the design fires for each scenario. A case study was conducted to demonstrate an application of this proposed method.     

A framework for Virtual Interactive Construction Education (VICE)

Training and process analysis in the construction industry has not taken full advantage of new technologies in simulation, modeling, and semantic web and software engineering. The purpose of this research is to develop a framework for a virtual interactive construction education system taking full advantage of these technologies. The modules will simulate the construction process for a facility from start to finish using information drawn from domain experts using real projects in the built environment. These modules can be used as training tools for new employees where they attempt to optimize time and cost in a virtual environment given a limited number of equipment, time and employee options. They can also be used as a process analysis tool before, during and after construction where a number of situational variables could be analyzed for exposure of potential risk. These modules would be particularly useful for repetitive construction where the initial project or task is analyzed for optimization and risk mitigation. This paper describes the framework using a residential construction example that is a 900 square foot (about 85 m²) wood frame single family house designed for the United States.     

Experimental Characterisation of the Fire Behaviour of Thermal Insulation Materials for a Performance-Based Design Methodology

A novel performance-based methodology for the quantitative fire safe design of building assemblies including insulation materials has recently been proposed. This approach is based on the definition of suitable thermal barriers in order to control the fire hazards imposed by the insulation. Under this framework, the concept of “critical temperature” has been used to define an initiating failure criterion for the insulation, so as to ensure there will be no significant contribution to the fire nor generation of hazardous gas effluents. This paper proposes a methodology to evaluate this “critical temperature” using as examples some of the most common insulation materials used for buildings in the EU market, i.e. rigid polyisocyanurate foam, rigid phenolic foam, rigid expanded polystyrene foam and low density flexible stone wool. A characterisation of these materials, based on a series of ad-hoc Cone Calorimeter and thermo-gravimetric experiments, serves to establish the rationale behind the quantification of the critical temperature. The temperature of the main peak of pyrolysis, obtained from differential thermo-gravimetric analysis under a nitrogen atmosphere at low heating rates, is proposed as the “critical temperature” for materials that do not significantly shrink and melt, i.e. charring insulation materials. For materials with shrinking and melting behaviour it is suggested that the melting point could be used as “critical temperature”. Conservative values of “critical temperature” proposed are 300°C for polyisocyanurate, 425°C for phenolic foam and 240°C for expanded polystyrene. The concept of a “critical temperature” for the low density stone wool is examined in the same manner and found to be non-applicable due to the inability to promote a flammable mixture. Additionally, thermal inertia values required for the performance-based methodology are obtained for PIR and PF using a novel approach, providing thermal inertia values within the range 4.5 to 6.5 × 10³ W² s K^?2 m^?4.     

区域火灾风险准则的确立研究

针对火灾生命损失风险从个体风险和社会风险两个方面，对区域火灾风险准则的确立进行了探讨。通过量化分析区域火灾风险的可容忍度，讨论了区域火灾风险的不可容忍风险线、审查线及可忽略线，为消防监督部门的风险决策提供基础框架，并结合上海市的相关数据，通过示例对区域火灾风险准则的确立作了说明。     

气雾剂火灾危险性分级方法研究

综述国内外气雾剂产品安全的相关研究,介绍气雾剂的火灾危险性及我国发生气雾剂火灾爆炸事故的情况。研究联合国橙皮书关于危险货物运输的建议书中关于气雾剂火灾危险性分级的试验内容,以及泡沫气雾剂、喷雾气雾剂的火灾危险性分级方法。在对此类方法研究的基础上,结合实际情况建立适宜我国经济发展和安全保障的气雾剂的火灾危险性分级方法,可以为相关行业标准的出台作技术性铺垫。     

Solar stills for production of distilled water

Solar stills have been designed to produce water for use in teaching and research laboratories. Various designs and configurations have been constructed and tested over the past 10 years. The original double-surfaced cascade stills (stills A and B) were constructed in aluminium and were rather expensive. Later models termed Series D and E were of galvanised mild steel with stainless steel distillate drains and safety overflow drains. These galvanised steel units suffered from severe corrosion after a few years of operation. The latest design series F, is built in aluminium with stainless steel distillate drains and automatic feed valves. All of the stills produce very pure distilled water (conductance ～1.5 × 10^?6 Ω^?1 cm^?1; pH 6.8–7.4) at a cost which is below that of conventional electrically heated stills.