Chamber tests chemical protective ensembles for leakage
Paul moves obediently to computer-controlled commands in his stainless-steel-enclosed home like a student in a self-defense or aerobic dance class.
Dressed for an attack with a simulated weapon of mass destruction, the animatronic manikin is trying out the new two-person Man In Simulant Test (MIST) chamber built at the U.S. Army Soldier Systems Center (Natick).
The MIST chamber, one of a handful designed for chemical simulant vapor testing, is intended to quickly and efficiently test complete prototype military chemical and biological agent protective ensembles for leakage with assistance from the manikin and human research volunteers.
Scientists and engineers at Natick will be able to save time and expense of sending their protective clothing to other chambers when a small on-site facility is all that’s needed.
“This gives us a compact car instead of an 18-wheeler,” said Walter Zukas, chemical engineer on the Chemical Technology Team. “It’s the perfect preliminary test chamber. You can tell right away if the prototypes are going to work.”
The range of ensembles spans from protective gear worn on the battlefield to the fully-encapsulated suits worn by first responders at a chemical spill. Because they’re not seamless outfits, it’s possible for vaporous contamination to enter through places such as zippers or where the trousers meet the overboots, which is why testing is necessary.
The chamber is divided into four rooms composed of insulated stainless steel walls similar to those found in industrial refrigerators and freezers. Snug door seals along with caulking and metal tape contain the simulated contaminant in the chamber.
Entry and exit is through the control room, which leads to the test pad recovery room, another room to decontaminate clothing, and finally the 9-foot by 10-foot test chamber. Connected outside the chamber is a unit that circulates temperature and humidity-controlled air inside the chamber. Each supporting room has a carbon trap filter to prevent contamination from the chamber during and after testing. The vapor from each test is fully recovered into the filters.
Thumb-sized detector Tenax patches are first placed strategically according to the garment on the manikin or human volunteers before donning the protective ensemble and proceeding through the series of motions.
Paul was developed by Creative Engineering, Inc. in Orlando, Fla., and the animatronic manikin is one of a few of its kind. It has a repertoire of moves that’s meant to test the ensemble’s closures and interfaces to the limit.
“(Paul) is programmed for 20 motions, but it can be changed,” said Axel Rodriguez, chemical engineer on the Chemical Technology Team. “We’re working to figure out a series of realistic sequences. They also will change depending on the garments.”
Human research testing may include activities with a stationary bicycle, treadmill, rowing machine and climbing machine, which are all good for stretching the garment to the point where it could leak, said Elizabeth Klemperer, chemist on the Chemical Technology Team and planner of the two-person MIST.
From the control room, one computer manages the animatronic manikin while another operates the carbon filter machines in the test chamber, records data and dispenses oil of wintergreen droplets from a syringe onto a heated plate that evaporate to create a simulated chemical gas environment.
“(Oil of wintergreen) is a really good representative of a wide variety of chemical agents because they tend to be high boiling liquids. It’s relatively non-toxic and easy to detect,” Zukas said. “We use a fraction of the amount of oil used at other facilities.”
Circulating air picks up the vapors, and plastic tubes inside the chamber bring air samples to a detector to check for even distribution. Vapor concentration is regulated by feedback to the carbon scrubber actuated by a signal from infrared detectors.
After a standard test period of two hours with constant chemical vapor exposure, the chamber is cleaned with filtered air heated to 150 degrees F to bring the chemical level to zero. The patches are then removed, capped in a bottle and analyzed in a laboratory at Natick.
Zukas said the Navy, U.S. Army Research Institute of Environmental Medicine and National Protection Center at Natick have expressed interest in the facility.
“It really could be used to test any equipment, including commercial items we’re interested in using. It’s like a climatic chambers but for a chemical environment, and without the rain and high wind,” Zukas said.