Issue 37: Firefighter Safety Research at the University of Maryland
By Marino DiMarzo, Ph.D.
In the immediate aftermath of 9/11, the University of Maryland, Department of Fire Protection Engineering joined forces with the Maryland Fire and Rescue Institute (MFRI) to establish the Center for Firefighter Safety Research and Development (the "Center"). The vision for the Center was to bring together first responders with the research community at the University of Maryland, thus creating and bringing to market innovative solutions enhancing firefighter safety. Each of the projects undertaken by the Center encompasses the following characteristics: a) it originates from a specific need of the first responders; b) it involves state-of-the-art-research; c) it results in the implementation and in-field testing of devices and techniques; d) it is completed with the commercialization of the successful products and dissemination of the effective techniques thus becoming readily available to the first responders.
Initial funding for the Center came from the National Fallen Firefighters Foundation. These funds resulted in a successful application to the Department of Homeland Security, Assistance to Firefighters Grant (AFG) in 2004. This first project focused on developing guidelines for firefighter's training. On any given day of the program three teams of four firefighters each performed a series of activities including: a standard fitness test, a maze evolution (where disorientation and physical challenges induced anxiety and emotional stress), a search and rescue fire evolution and a long term exposure to near flashover conditions with subsequent fire suppression. A total of 208 firefighters participated in the study. Each participant was continuously monitored with the LifeShirt System. This is an ambulatory, multisensory, continuous monitoring system for collecting analyzing and reporting data. The vital signs collected included: core body temperature (with an ingestible radio transmitter thermometer), pulmonary functions, Electrocardiogram (ECG), individual activity/posture, blood oxygen saturation, and skin surface temperature in the chest area. Additional testing (Urine Specific Gravity test to determine the level of hydration and blood pressure measurements) were performed at specific times during the day. The environment in the fire room during the long term exposure to near flashover conditions was closely monitored by extensive thermocouple rakes, flux gauges video and infrared (IR) cameras. Significant outcomes of the study highlighted the need for proper hydration of the firefighters (about 152 of the subjects started the day in poor hydration conditions while only 31 were properly hydrated out of 208 participants). The thermal performance data identified a surprising long time delay associated with thermal behavior of the turnout gear. These findings prompted further investigations.
The subsequent application to the AFG focused mainly on firefighter's location and on turnout gear performance. The firefighter's location technology was developed making use of a combination of GPS, dead-reckoning, and directional signal strength detector. This approach provided a seamless transition from outdoor to indoor and enabled effective search and rescue technology which is presently being commercialized by TRX, Inc. This company benefited from the University of Maryland business incubator and is now a full-fledged business focusing on a variety of technologies assisting first responders.
The turnout gear thermal performance studies encompassed a 36 firefighter program where each subject was exposed to significant heat flux and hot gasses from a fire. Data from thermocouples placed on each individual allowed for the validation of a computer model for the prediction of the transient thermal performance of the gear. This model used physical and thermal properties associated with each of the layers constituting the turnout gear assembly. Air gaps are created between garment layers. As an example, a significant air gap exists between the turnout gear coat and the tee-shirt or between coat outer layer and the insulating batting material. The role of these air gaps in the gear was characterized in detail and their impact on the overall thermal performance were quantified.
Over the past five years, cooperative research sponsored by the U.S. Navy was conducted at MFRI with the objective of characterizing the physiological response of firefighter exertion while exposed to a severe fire environment. One of the major conclusions of these studies highlighted the significant impact of moisture content on turnout gear performance. The testing encompassed a number of repeated exposures of the same group of individuals to identical fire conditions. The subjects were interviewed after each exposure and were questioned on the perceived fire intensity during the test. Those individuals that donned dry undergarments perceived the fire to be less intense than those individuals that were wearing the same undergarments after previous exposures. The reason for this significant difference in performance of the turnout gear is twofold. First, the moisture content in the gear is high for the case of repeated exposures. In this case, the insulating layer in the gear exhibits an increased thermal conductivity. Second, the moisture in the region near the gear outer layer is subjected to high temperatures. This results in a significant vapor generation and the vapor can then easily migrate to the coldest region in the layer, namely at the subject skin. There the steam condenses depositing heat and possibly causing burn injuries.
In 2009, the Navy initiated a study to determine the effectiveness of hand and forearm immersion on decreasing core body temperature using varying water temperatures. Volunteers will complete an exercise regimen (e.g., standard firefighter's agility test, training scenarios, or other equivalent physical activity such as, but not limited to, hose dragging, mannequin dragging, stair climbing, equipment carry, etc.) to increase body core temperature and then various cooling methods will be applied. Cooling methods will include submersion of the hands and forearms in water at various temperatures. Core and skin temperatures, ECG, respiration, weight, and subjective assessments will be collected prior to and throughout exposure to exercise and cooling.
Again in 2009, a new round of funding from DHS-AFG was successfully secured to develop a computer model for the design of turnout gear. The objectives of the proposed research are to develop a sound theoretical and experimental program to quantify the difference in performance of the present generation gear and of the modified gear proposed here. These studies will be complemented with an extensive in-the-field testing program with a statistically relevant set of subjects. The research team is composed of fire protection engineers providing heat transfer modeling as well as coordination and management of the program, mechanical engineers developing measuring techniques and laboratory based experiments to quantify the gear performance in controlled settings, Lion Apparel manufacturer to develop and integrate novel design features in the gear as appropriate, and finally MFRI personnel and volunteers to test and quantify the performance of the advanced gear in the field.
This effort in conjunction with Lion Apparel will enable the manufacturer to optimize the layering of the turnout gear assembly prior to actually developing physical prototypes. Extensive experimental investigation of the moisture movement between the garment layers will provide data for the model validation. Furthermore, smart firefighter garments may be developed in order to mitigate burns and manage the humidity transport inside the garments. The smart garments will rely in their operation on shape memory fibers (SMF) which are inter-woven with the garment fabric. The SMF are passively activated whenever excessive thermal exposures are detected because of their unique phase transformation characteristics. Once activated, the SMF will introduce air pockets in the garments that will reduce their thermal conductivity and hence mitigate the possibilities of occurrence of burns.
Marino DiMarzo is with the University of Maryland
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