Measurements of Smoke Characteristics in HVAC Ducts

Research paper published in the journal Fire Technology in 2001The characteristics of smoke traveling in an HVAC duct have been observed along with the response of selected duct smoke detectors. The simulated HVAC system consists of a 9 m long duct, 0.45 m in diameter. An exhaust fan is placed at one end of the duct and is capable of inducing airflow rates that range from 0 to 1.5 m 3 /s. The flow is controlled by means of a manual damper. On the upstream end of the duct there is a square exhaust hood approximately 2.2 m at the bottom and 0.3 m at the top. The bottom of the hood is approximately 2.5 m above the floor a shroud extends down to approximately 1.5 m above the floor. The test section, placed immediately downstream of the hood, is 3.5 m long duct with a square cross section of 0.4 m on a side. The instrumentation includes oxygen, carbon monoxide and carbon dioxide gas analyzers and a load cell to determine the energy release rate of the fires tested. The smoke within the duct is characterized by means of a laser light sheet and CCD camera, two white light source and photocell ensembles, a Pitot tube and an array of eight thermocouples placed on the vertical plane of symmetry. A smoke detector was placed at the downstream end of the test section. Two types of detectors were tested, ionization and photoelectric, with a single sampling probe geometry. The fires tested cover a wide range of fuels (propane, heptane, toluene, toluene/heptane mixture, shredded paper, polyurethane foam, wood cribs) with the peak energy release rates up to 800 kW. The smoke detector performance, temperature, flow field, smoke particle size and particle distributions are dependent on the fire characteristics and airflow through the duct. The different measurements could be scaled by means of the fire size and airflow rate but left a strong dependency on the fuel and burning characteristics (i.e. smoldering, flaming). The optical density and mass optical density are analyzed as metrics for characterizing smoke and smoke detector response. Detailed comparisons between the different metrics used are presented throughout this work. Clear evidence of stratification and aging of the smoke along the duct are also presented. The limitations of the present configuration and the need for a larger scale study are also discussed

A Priori Modelling of Fire Test One

Chapter 10 in the book: The Dalmarnock Fire Tests: Experiments and Modelling, Edited by G. Rein, C. Abecassis Empis and R. Carvel, Published by the School of Engineering and Electronics, University of Edinburgh, 2007. ISBN 978-0-9557497-0-4An international round-robin study of fire modelling was conducted prior to the Dalmarnock Fire Tests in order to assess the state-of-the-art of fire modelling in real scenarios. The philosophy behind the Dalmarnock Fire Tests was to provide instrumentation density suitable for comparison to field models and designed the scenario for maximum test reproducibility. Each participating team independently simulated a priori the test using a common detailed description of the compartment geometry, fuel packages, ignition source and ventilation conditions. The aim of the exercise was to forecast the test results as accurately as possible, and not to provide an engineering analysis with adequate conservative assumptions or safety factors. The modelling results and experimental measurements are compared among themselves, allowing for conclusions on the robustness, reliability and accuracy of current modelling practices. The results indicate large scatter and considerable disparity among predicted fires and also differing from the experimental data. The Dalmarnock Fire Test One was benchmarked against a second test to establish the potential experimental variability. The scatter of the simulations is much larger than the experimental error and the experimental variability. The study emphasises on the inherent difficulty of predicting fire dynamics and demonstrates that the main source of scatter is originated in the many degrees of freedom and the uncertainty in the input parameters. The conclusions from the study are made public to encourage debate and exchange of views on the topic of fire modelling

Round-robin study of a priori modelling predictions of the Dalmarnock Fire Test One

Peer-reviewed journal paper published in 2009 about the international modelling exercise conducted in 2006.An international study of fire modelling was conducted prior to the Dalmarnock Fire Test One in order to assess the state-of-the-art of fire simulations using a round-robin approach. This test forms part of the Dalmarnock Fire Tests, a series of experiments conducted in 2006 in a high-rise building. The philosophy behind the tests was to provide measurements in a realistic fire scenario involving multiple fuel packages and non-trivial fire growth, and with an instrumentation density suitable for comparison with computational fluid dynamics models. Each of the seven round-robin teams independently simulated the test scenario a priori using a common detailed description of the compartment geometry, fuel packages, ignition source and ventilation conditions. The aim of the exercise was to forecast the fire development as accurately as possible and compare the results. The aim was not to provide an engineering analysis with conservative assumptions or safety factors. Comparison of the modelling results shows a large scatter and considerable disparity among the predictions, and between predictions and experimental measurements. The scatter of the simulations is much larger than the error and variability expected in the experiments. The study emphasises on the inherent difficulty of modelling fire dynamics in complex fire scenarios like Dalmarnock, and shows that the accuracy to predict fire growth (i.e. evolution of the heat released rate) is, in general, poor

Guidelines for Diagnosis and Management of Infective Endocarditis in Adults: A WikiGuidelines Group Consensus Statement.

IMPORTANCE Practice guidelines often provide recommendations in which the strength of the recommendation is dissociated from the quality of the evidence. OBJECTIVE To create a clinical guideline for the diagnosis and management of adult bacterial infective endocarditis (IE) that addresses the gap between the evidence and recommendation strength. EVIDENCE REVIEW This consensus statement and systematic review applied an approach previously established by the WikiGuidelines Group to construct collaborative clinical guidelines. In April 2022 a call to new and existing members was released electronically (social media and email) for the next WikiGuidelines topic, and subsequently, topics and questions related to the diagnosis and management of adult bacterial IE were crowdsourced and prioritized by vote. For each topic, PubMed literature searches were conducted including all years and languages. Evidence was reported according to the WikiGuidelines charter: clear recommendations were established only when reproducible, prospective, controlled studies provided hypothesis-confirming evidence. In the absence of such data, clinical reviews were crafted discussing the risks and benefits of different approaches. FINDINGS A total of 51 members from 10 countries reviewed 587 articles and submitted information relevant to 4 sections: establishing the diagnosis of IE (9 questions); multidisciplinary IE teams (1 question); prophylaxis (2 questions); and treatment (5 questions). Of 17 unique questions, a clear recommendation could only be provided for 1 question: 3 randomized clinical trials have established that oral transitional therapy is at least as effective as intravenous (IV)-only therapy for the treatment of IE. Clinical reviews were generated for the remaining questions. CONCLUSIONS AND RELEVANCE In this consensus statement that applied the WikiGuideline method for clinical guideline development, oral transitional therapy was at least as effective as IV-only therapy for the treatment of IE. Several randomized clinical trials are underway to inform other areas of practice, and further research is needed

Use of Sensors for Fire Detection and Monitoring

The ultimate goal of placing fire detection systems in buildings and structures is to allow for the rapid detection of fire and accurate prediction of ensuing fire behavior. Through a-priori prediction of how a fire might evolve, relevant information can be delivered to the appropriate stakeholders. In the near-term, development of detection systems which detect fire events more quickly, with better discrimination against nuisance and false alarms, and allow real-time monitoring of the state of a fire is a critical interim step. If we are able to detect fires earlier than is presently possible, loss of life, injuries and property damage may be drastically reduced. In addition, if earlier detection is simultaneously paired with collection of better information on the spatial location of the fire, and its stage of development, this information can be delivered to emergency first responders. Emergency response planning and actions can then be targeted such that appropriate resources are applied earlier in a fire situation. This will further reduce the potential for loss of life and injury to both occupants and first responders, as well capital losses due to fire. The advent of building monitoring systems affords excellent potential to improve upon current fire detection protocols. Building systems incorporate a large quantity of different sensors for a variety of uses. Currently, most building sensors are focused primarily on the parameters necessary to optimize building efficiency and on intrusion detection, but they are installed at much higher density than standard fire detectors and the density is increasing as greater efficiencies in cost and quicker return on investment can be achieved. While most of these sensors are presently chosen to fulfill building management purposes, there is significant opportunity to integrate some of the existing sensors, or to develop new sensors of similar type, for applications in systems for rapid fire detection, real-time fire monitoring, and potentially fire forecasting. Leveraging building environmental and other sensors for this expanded use, however, requires further knowledge about the characteristics of fires, from ignition to full growth, specifically with regards to those physical characteristics which might be measured by any new fire detection sensor suites. One of the biggest challenges associated with development of new fire detection systems is their associated cost and the reluctance on the part of building owners, insurers, and other parties to invest in detection systems when fire is such a rare event. Thus while there has been research into improved fire detection technology, there has been limited advancement in detection system design. Ultimately, the limiting factors around potential use of building monitoring sensors for this purpose will relate to determination of optimal sensor response to various signals generated by a developing fire and optimal sensor density in terms of cost versus position of sensors relative to potential fire sources. One of the best chances for improved fire detection, as well as potentially for reduced nuisance alarms and enhanced fire monitoring, is to first take advantage of the signals transmitted by building sensors and assess their potential for use in fire detection. Therefore the objectives of this research were to characterize fire and non-fire environments using a range of sensor technologies to determine potential characterization parameters and to evaluate background and nuisance sensor response using the same sensor technologies; to identify candidate sensors and develop an “idealized” sensor block; and finally to develop algorithms for fire state determination. Approximately 125 experiments were performed in a range of environments ranging from a 1m^3 box to full-scale experiments in a two-story structure. Temperature, relative humidity, and luminosity were measured during all experiments, while heat flux and heat release rate were additionally measured during the full-scale experiments. The research shows that fire signals measured using non-fire sensors could be distinguished from background and nuisance signals indicating their potential for use in improved fire state determination. The data collected, in particular with regards to luminosity and relative humidity, has not been previously reported in the literature and thus provides new information that may be leveraged for incipient fire detection and monitoring. Furthermore a novel learning algorithm, hierarchical temporal memory, a real-time continuous learning algorithm yielded promising results for fire state determination. Real-time data streaming of the sensor data paired with the hierarchical temporal memory yielded the ability to rapidly identify fire anomalies

Flammability of solid materials: An experimental calorimetric approach

Flammability properties of solid materials are necessary to be a known parameter for many purposes: among them, forensic investigations of fire and explosion events, fire risk or hazard analysis, design and development of combustion-based systems. However, despite the large quantity of data in the literature, the flammability properties of many materials still appear not to be available or show a degree of uncertainty associated with them, which makes their value limited. The present work is aimed at proposing a calorimetric-based approach to determine some flammability and thermophysical properties of solids, with specific regard to time-to-ignition as a function of the imposed heat flux. Plastic materials have been here chosen as test cases, even though this approach has a general applicability. The two mentioned parameters have been analyzed to provide a quantitative estimation of the critical heat flux (minimum heat flux resulting in ignition). A cone calorimeter has been employed to conduct the experiments: the facility complies with standard ASTM E 1354; the related uncertainty and validity range has been evaluated through an appropriate error analysis. Finally, thermal inertia has been thereby calculated for the considered materials through a simple thermodynamic model, which is based upon critical heat flux and energy conservation. Copyright \uc2\ua9 2011 by ASME