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Smart Firefighter Garment
(Sponsor: Department of Homeland Security)
Novel turnout gear technology is proposed including Shape Memory Fibers enabling the thermal management of the gear in standby situations while retaining full protection when exposed to fire. Also proposed is upgrading a micro-computer technology, which was developed by a previous DHS grant for the monitoring of thermal exposure, to predict also the humidity transport in the gear and communicating excessive thermal loads to the firefighter during operation. Particular emphasis will be placed on the development of turnout gear design tools to support and enhance manufactures innovation. The proposed research will be implemented by a multi-disciplinary team that includes the Fire Protection and Mechanical Engineering Departments at the University of Maryland (UM) for concept development and laboratory testing, Maryland Fire and Rescue Institute (MFRI) for in-field testing and evaluation, and Lion Apparel, Inc. for manufacturing the smart garments.
The main approach adopted in this study to implement the objectives for the three year project is as follows:
- Extend the mathematical model to include moisture and steam behavior within the air gaps and within the different layer of material in the turnout gear.
- Test a variety of layer configurations common in available turnout gear and in new configuration developed in consultation with Lion Apparel, Inc.
- Validate the mathematical model with the experimental results and construct a robust widely applicable model with an extensive database of material physical and thermal properties.
- Continue to develop and test new gear configurations in consultation with Lions Apparel, Inc.
- Design and implement SMF in new gear configuration optimizing placement and operation to maximize performance in a variety of conditions
- Implement in the mathematical models the SMF behavior to provide support to guidance in the performance optimization processes
- Implement the integrated exposure microcomputer in the turnout gear.
- Test the microcomputer prototype at MFRI to demonstrate its use and firefighter safety enhancement.
- Consult extensively with Lion Apparel to design new turnout gear configurations that implement the technologies developed during the research program.
The concept of the proposed smart garment can best be understood by considering the schematic drawings displayed in the figure below. At low ambient temperatures, the smart garment assumes the configuration shown in Figure (a). In such a configuration, the Shape Memory Fibers (SMF) are impregnated inside the thermal insulation layer is such a way that results in no air pockets. Once the firefighter enters the fire scene and gets exposed to moderate temperatures, the SMF starts undergoing its unique phase transformation and begins expanding generating an air pocket as shown in Figure (b). In this manner, the garment thermal insulation characteristics are enhanced reducing the heat flow from the fire to the firefighter skin. This will make the firefighter less susceptible to burn injuries.
With further exposures to excessively high temperatures, the SMF expand more generating larger air pockets as shown in Figure (c). Such capabilities are achieved completely passively by proper training of the SMF to complete its phase transformation at excessively high temperatures which are within the safe norms acceptable by the firefighting standards.
Proposed Smart Garment
A sweating hotplate developed by Measurements Technology Northwest, Seattle, WA is used. The hotplate, often referred to as the “skin model”, produces accurate, repeatable measurements of the thermal resistance and vapor permeability of textiles. This system was designed in accordance with ISO 11092 and ASTM F1868 to measure both thermal characteristics. The sweat plate is shown in the figure below.
Photographs of the sweating hotplate experimental set-up
The figure below shows the layout of the proposed garment which is made of four layers. Two outer shell layers consisting of PBI-Kevlar matrix (#1) and Fusion Nomex-Kevlar blend (#3), a moisture barrier (#5) made of A&B cross stitch film on Nomex face, and Sempri Nomex thermal layer (#8).
Figure (a) shows a garment without air pockets. Figure (b) shows a garment with air pocket of ¼” which is introduced between the thermal liner and the moisture barrier. An acrylic frame of ¼” thickness is used to introduce the air pocket. The fabrics of the different layers of the garment are stretched around the frame to avoid any sagging. Figure (c) shows the garment with air pocket of ½ “ which is generated by using two acrylic frames each has a thickness of ¼”.
Photographs of the garment with and without air garments
The figure below displays the thermal resistance of the conventional garment with and without air pockets of different sizes. The results are obtained by conducting four sets of experiments in order to calculate an average thermal resistance for the considered three air pocket sizes.
Thermal resistance of the garment with and without air pockets of different sizes
The obtained results indicate clearly that introducing the air pockets increases considerably the thermal resistance of the garment.
Temperature and Humidity Exposure Computer
A new class of a wireless Heads Up Display (HUD) is developed to provide the firefighters with continuous monitoring of their body and gear temperatures. The proposed HUD aims at providing the firefighters with early warning visual signals whenever these temperatures approach critical safety thresholds. Upon receiving these warning signals, the firefighters must exit the fire scene before endangering their lives. The HUD warning functions are programmable and can be modified according to the type of gear that the firefighter is wearing. It can also operate with either continuous or flashing displays to provide adequate warning and ensure saving the power necessary to drive the displays. The proposed HUD has been tested by nine firefighters wearing several types of gears at the Maryland Fire and Rescue Institute (MFRI).
The developed HUD will comply with the latest NFPA-1981 2002 Edition Standards.
One important aspect of firefighters’ safety is to avoid excessive exposure to high temperatures which may result from either prolonged stay in the fire scene or inadequate insulation as provided by the gear. For a typical evolution, the figure below shows that the potential of exposure to excessive temperatures may occur after the firefighter has already departed the fire scene. Accordingly, it is essential to provide the firefighter with a device that can continuously monitor his gear and body temperatures, predict the excessive temperatures that may occur due to prolonged exposures, and provide him with early warning signals to depart safely the fire scene.
The device which is in effect is an “exposure computer” is interfaced with the heads up displays of the firefighters to provide the warning signal by energizing the light emitting diodes (LEDs) of these HUD.
Typical ambient and body temperature profiles during firefighting operations
The figure below shows examples of typical HUD which are commercially available and are used for warning the firefighters about the status of their air supply pressure.
The figure below shows a photograph of version 1 of a prototype of the developed HUD and the main components of the exposure computer.
A photograph of a prototype of the developed HUD
Photographs of the components of the developed version 1 HUD
The computer fits inside the SCBA and is protected by tank as shown below. Further more, it has an automatic on-off thermal switch that activates it when the firefighter enters the fire scene and deactivates when leaves it in order to save the battery life.
Photographs of the components of the developed HUD
The figure below shows the UMD-HUD during testing by firefighters at MFRI.
The UMD-HUD during testing by firefighters at MFRI
Typical output temperatures which are recorded by the exposure computer are shown below:
Typical output temperatures
The figure below displays the temperature distribution at different heights above the floor of the burn house inside MFRI’s facilities.
Fire training environment
Below are displays of the inside and outside temperatures of the gear as measured during all the tests. The scatter in the data is due to the different gear configurations. For example, firefighters wearing Tee shirts experience faster thermal response whereas firefighters wearing sweat shirts experience delayed thermal response.
The inside and outside temperatures of the gear
It is paramount to provide the firefighter with information and warning about thermal exposure inside firefighting environment. A real time exposure computer with HUD that relies in its operation on measured gear surface temperature could calculate immediately that prolonged exposure in the firefighting environment may cause excessive temperatures in the gear at a later time. Further, such a device could provide a calculated maximum allowable residence time based on the thermal history of the gear during the evolution. This information would refer to the gear status in the same way as the air pressure refers to the time available with the breathing apparatus
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