Predicting Mechanical Strength of In-Use Firefighter Protective Clothing Using Near-Infrared Spectroscopy

The exact lifespan of in-use firefighter protective clothing is difficult to predict due to the large variations in use between individual garments. Furthermore, testing methods used to evaluate new protective clothing are destructive in nature and could not be applied to in-use garments. Various non-destructive techniques have been proposed for the evaluation of in-use clothing, each possessing its own advantages and disadvantages. The ability of near-infrared spectroscopy to predict the tensile strength of thermally aged fabrics used in protective clothing for wildland firefighters and other workers is investigated here. Fabrics were exposed to heat fluxes from 10 kW/m² to 40 kW/m² for various durations using the cone calorimeter, after which the tensile strength of the fabrics was measured. Temperatures measured during the exposures and results of thermal gravimetric analysis tests were used to interpret changes in tensile strength. Multivariate linear regression was used to develop correlations between the tensile strength and the reflectance values measured between 1500 nm and 2500 nm for new and thermally aged fabrics. It was found that models based on reflectance measurements made at as few as three wavelengths could be used to estimate the tensile strength of the thermally aged specimens.     

Test method for evaluating fabric flammability and predicted skin burn injury in microgravity

To address fire safety concerns associated with the use of flammable fabrics during space travel, an apparatus was designed to be flown on low-gravity parabolic aircraft flights in order to assess the flammability of cotton and 50% cotton/50% polyester fabrics, and the resulting skin burn injury that would occur if these fabrics were to ignite. The apparatus, modelled after a standard fabric flammability test, was also used on the ground for experiments under earth’s gravity. Variables examined in the tests include gravity level, fabric type, air gap size, and orientation of the fabric. Flame spread rates, heat fluxes, and skin burn predictions determined from test results were compared under the two gravity levels. The orientation of the fabric had a large effect on flame spread rates, heat fluxes and predicted skin burn times for tests conducted under earth’s gravity. Flame spread rates and heat fluxes were highest when the fabric was held in the vertical orientation, which resulted in the lowest predicted times to produce skin burns. Flame spread rates and heat fluxes were considerably lower in microgravity than under earth’s gravity, which resulted in longer predicted times to produce skin burns.     

Research in Protective Clothing for Firefighters: State of the Art and Future Directions

This paper presents a summary of documented research into protective clothing for firefighters. Particular emphasis is placed on research into estimating the useful life of this clothing and the development of test standards for evaluating its thermal protection. Other areas covered in this review include moisture transfer in clothing, heat stress, design criteria, chemical protective clothing, and heat transfer modeling of protective clothing. Recommendations for future protective clothing research are also presented.     

An analysis of two-heater active thermal control technology for device class testing

A novel technology for controlling temperature rise in the class testing is described in this article. This technology is based on two active heater sources and is called a two-heater active thermal control (2H-ATC) system. From a point of control, a lumped analytical model for representing the whole class testing process is very important, and is developed in this article. The model was validated by comparing the simulated result with the measured result on a commercial tester. Based on this model, we have studied the issue of optimization of the performance of the testing process, in particular examining effects of test system parameters on system performance. We have also observed a concept called critical heater power, which is important in achieving a minimum overshoot at the transition from the preheating stage to the testing stage. The outcome of this study has already been applied in practical process control during the whole class testing.     

Heat Transfer Model of Flame Resistant Fabrics During Cooling After Exposure to Fire

Protective clothing is used in many industries to protect firefighters and other workers from fire and other hazards. While skin burns can occur during a fire, protective fabric temperatures remain high for some time even after a fire ends. Therefore, skin burn injuries can occur during the time in which a fabric is cooling. A heat transfer model has been developed that can predict inherently flame resistant fabric temperatures and skin burn injuries during this cooling phase. This paper describes the heat transfer model, including methods used to calculate the apparent heat capacity and the convection heat transfer coefficient as the fabric cools. The new model has been validated using data from bench top tests of Kevlar®/PBI fabric specimens. Parametric studies using the model demonstrate the importance of selected thermal properties and boundary conditions on fabric temperatures and bench top test results.     

Testing and modelling of a novel ceiling panel for maintaining space relative humidity by moisture transfer

Radiant ceiling panels are preferred over all-air systems because of their ability to lower energy consumption and maintain better comfort conditions. One disadvantage is their inability to moderate indoor humidity. To overcome this limitation, a new panel that can transfer heat and moisture is being developed. This research determines the performance of this panel under different temperature and humidity conditions. The effectiveness of the panel ranges from 15% to 28%, depending on the conditions. A computational fluid dynamics model of the panel has been developed using the commercial software, FLUENT. Good agreement is seen between experiments and the model for most cases. Comparing the change in humidity ratio of the air, the average difference is 5%.     

Assessment of Factors Affecting the Continuing Performance of Firefighters’ Protective Clothing: A Literature Review

There has been some research into the level of damage and changes to important properties of firefighters’ protective clothing after exposure to conditions such as elevated temperature and ultra violet radiation. However, at this time, the results are not comprehensive enough to develop a standard procedure to estimate the remaining useful life of firefighters’ protective clothing. There is also a need to develop non-destructive techniques to evaluate clothing, for most tests used to evaluate properties of clothing are destructive, and visual cues cannot completely assess the level of deterioration of the properties of thermal protective fabrics. In this paper, major factors that affect the continuing performance of firefighters’ protective clothing and their effects on the service life of the clothing are reviewed. Some non-destructive methods which have been employed in different studies to evaluate the degradation of physical properties of firefighters’ protective clothing are also described, along with statistical and probabilistic methods for estimating the useful life of materials. Suggestions for future research, which will assist fire departments in determining the level of damage to clothing, and estimating its remaining useful life are also discussed.     

Evaluating Models for Predicting Full-Scale Fire Behaviour of Polyurethane Foam Using Cone Calorimeter Data

Two models that can be used to predict full-scale heat release rates of polyurethane foam slabs were evaluated in this study. Predictions were compared with results of furniture calorimeter tests of 10 cm thick polyurethane foam specimens which were ignited in the centre or on the edge. Furniture calorimeter results indicated that peak heat release rates and fire growth rates were higher during centre ignition tests than edge ignition tests. For both situations, the growth phase of the heat release rate curves measured in the full-scale tests was successfully predicted using t ² design fires; the choice of a specific t ² fire depended on the surface area of the specimen and ignition location. A model originally developed during the European Combustion Behaviour of Upholstered Furniture (CBUF) project was also evaluated using heat release rate data from cone calorimeter tests and flame area burning rates measured using infrared video records of the furniture calorimeter tests. This model was able to successfully predict the initial growth phase of the fires and predictions of peak heat release rates were within 17% of measured values. The model had less success in predicting heat release rates later in the growth phase and during the decay phase of the fires, and did not appear to capture all of the physics of the full-scale tests, in particular foam melting and subsequent liquid pool burning. As the model did show promise, future work is planned to address these shortcomings and to develop improved flame spread models for polyurethane foam.     

“Engineering Graduate Teaching Assistant Instructional Programs: Training Tomorrow's Faculty Members”

Although there has been increased interest in graduate teaching assistant (GTA) training programs recently, few examples of programs specifically for engineering GTA's are found in the technical literature. A survey of engineering schools in Western Canada and the Pacific Northwest region of the United States has been conducted to determine the extent of instructional programs. The results of this survey and the literature indicate that there are large differences in the amount of training that GTA's in different engineering schools receive. While some are involved in extensive training programs, many receive little or no instruction in teaching, and/or inadequate feedback to help improve their teaching skills. These findings are discussed, along with details of innovative instructional programs found in the literature, and suggestions for improving the state of engineering GTA instruction.