ABERDEEN PROVING GROUND, Md. (May 14, 2015) -- Army researchers recently developed and patented a new test fixture and experimental method, named the Low-volatility Agent Permeation method. Permeation is the penetration of a permeate, in this case a lethal chemical agent, through a solid.
The U.S. Army Edgewood Chemical Biological Center developed the test method, which is on track to become a U.S. Department of Defense official test and evaluation method for chemical agent or VX permeation through protective equipment. A U.S. patent on the LVAP fixture and method is expected soon.
The method built upon multiple years of ECBC research, with support from the Joint Science and Technology Office, U.S. Army Natick Soldier Research and Development Center, Deputy Under Secretary of the Army for Test and Evaluation and the Joint Project Manager for Protection.
LVAP is a great success story in demonstrating the power of collaboration. The research and development of LVAP began within ECBC's Operational Toxicology Branch. ECBC's Decontamination Sciences Branch supported the understanding of permeation with M&S. The permeation experiments, development, and most of the laboratory work was conducted within ECBC's Permeation and Analytical Solutions Branch. This LVAP method is now being transitioned to ECBC partners at the West Desert Test Center at Dugway Proving Ground.
LVAP has shown increased accuracy for measuring the permeation of low-volatility contaminants, such as VX. LVAP is a contact-based method, using a sorbent pad to collect the total permeated mass of contaminant. A weight is applied to the fixture, ensuring that all layers are in good contact. This weight corresponds to 1 psi, which is consistent with the pressure used when grasping an object with the hand.
Traditional methods of measuring permeation are dependent on collecting vapors of the permeated contaminant. This can be less accurate for low-volatility contaminants, since the vapor concentration may not represent the potential hazard that has permeated through.
LVAP has recently completed an official verification and validation, under the auspices of DUSA TE. Using standard ISO calculation, the V&V documented the variability of the method to be +/-8.2 percent, which is much improved from the +/-80 percent for similar materials using a traditional permeation method. LVAP is awaiting final transition, expected Spring 2015, when the T&E community formally accept LVAP as a method for Acquisition-level testing.
As part of the V&V study, a physics-based model was developed to predict neat agent permeation through the test materials. This was based on a Fickian diffusion model with the diffusivity and solubility of VX in the latex material estimated by correlation with published values. The model was successful in predicting the measured permeation for VX through latex at the 24 hour and 48 hour time points, prior to the experiments being conducted. This modeling effort was conducted in collaboration with scientists from the Decontamination Sciences Branch.
"The modeling of this method was remarkable," said Dr. Terrence D'Onofrio, principal investigator for this research. "We can describe how VX interacts with different materials, and predict how much will come through over time, using these physics-based approaches."
The M&S can predict the levels of permeation that occur over time, guiding experiments to the enable focus on critical time points. The modeling also enables comparison with data obtained by traditional vapor-collection methods.
"This ability to predict the changes over time fills a huge gap from the previous methods," says D'Onofrio.
LVAP has already had an impact on personal protective equipment and laboratory procedures used at ECBC. D'Onofrio and his colleagues within ECBC's Engineering Directorate used LVAP as part of a safety initiative to test laboratory gloves against high-concentration VX solutions. Through the use of LVAP, they were able to demonstrate that the gloves offered protection for the laboratory scenario tested. The Technical Report of this research will be used to update the lab procedures and safety training.
Beyond DOD, domestic elements such as the Federal Bureau of Investigation and the Department of Homeland Security, have discussed using LVAP to test their First Responder suits. British Agencies have also expressed interest in the method.
An official ceremony recognizing LVAP as a program and test method of choice for the DOD is scheduled for later this year.
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The Edgewood Chemical Biological Center is part of the U.S. Army Research, Development and Engineering Command, which has the mission to empower the Army and joint warfighter with technology and engineering solutions that ensure decisive capabilities for unified land operations. RDECOM is a major subordinate command of the U.S. Army Materiel Command.
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