Grantee Research Project Results

Final Report: Decontamination Wipes for First Responders

EPA Contract Number: EPD08031
Title: Decontamination Wipes for First Responders
Investigators: Kaiser, Robert
Small Business: Entropic Systems Inc.
EPA Contact: Richards, April
Phase: I
Project Period: March 1, 2008 through August 31, 2008
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2008) RFA Text |  Recipients Lists
Research Category: SBIR - Homeland Security , Small Business Innovation Research (SBIR)

Description:

The threat of chemical or biological (CB) attack is real. During a CB emergency, first responder units are critical for handling the emergency, and then restoring the environment where it occurred. After a threat has been contained, the first responders must decontaminate themselves along with their equipment. The decontamination products currently commercially available do not provide simple and practical means of doing so.

Entropic Systems Inc. (ESI), with the Edgewood Chemical and Biological Command (ECBC), has been developing a decontamination wipe for the immediate decontamination of chemical warfare agents (CWAs) from sensitive military equipment. The result of this work is an absorptive/adsorptive decontamination wipe that effectively removes greater than 90 percent of CWAs from a variety of sensitive equipment items in one pass. This wipe decontamination system is easy to use, highly transportable, requires no capital equipment investment, little or no training, and no additional resources to be effective. However, in order to be of utility to first responders, these wipes must be able to achieve significantly higher decontamination levels than those required by hasty decontamination.

The objectives of the Phase I program were to:

• Demonstrate that wiping with absorptive/adsorptive wipes will effectively decontaminate liquid simulants to below the IDLH airborne exposure levels of the corresponding CWA, from coupons of substrates that are commonly found on first responder equipment.
• Perform wiping tests on representative first responder equipment to demonstrate that wiping can effectively decontaminate objects with complex geometries.
• Demonstrate low off-gassing of used wipes.
• Demonstrate the potential of the spray and wipe process for spore removal.
• Optimize wipe design and wiping procedures.

Summary/Accomplishments (Outputs/Outcomes):

ESI believes that all the objectives of the program were met while, at the same time, demonstrating that it may not be possible to decontaminate a piece of equipment to IDLH levels by wiping with a wetted adsorbent wiper, as originally contemplated. Wipers are a very effective means of removing surface contamination from impermeable, non-porous, and non-absorbent solid surfaces (i.e., metals) where the contaminant remains on the surface. As the substrate becomes more permeable, more porous, and more absorbent, wiping effectiveness decreases as the amount of contaminant migrating into the sub-surface solid structure increases. With such surfaces, wiping will not reduce the contamination levels required to reach IDLH levels for very toxic contaminants. The problem is rendered worse when the contaminated object has an irregular surface that prevents a wiper, even a wetted wiper, from coming into contact with all of the contaminant present.

While attaining the high levels of decontamination required to allow equipment to be reused safely may not be achievable with a wetted adsorbent wiper, this goal is attainable by a process that uses the same tools as wiping, but in a different way, and which ESI has called diffusion cleaning (patent pending). The principle on which diffusion cleaning is based is the transfer by molecular diffusion of a contaminant from a contaminated surface (i.e., the source) to an adsorbent that traps the contaminant (i.e., the sink). These requirements are met by wrapping a contaminated object in activated carbon fabric wetted with HFE-7200 and placing these items in a resealable plastic bag. In less than one day, the contaminant is removed from the contaminated surface, and transferred to the activated carbon fabric, where it is trapped in the pores.

There is significantly less diethyl methyl phosphonate (DEMP) off-gassing from either polycarbonate or CARC coupons, initially contaminated with DEMP, that were immersed for extended periods of time in HFE-7200 in the presence of either activated carbon fabric (ACF) or non-adsorbent polyester fabric (PerfectClean) fabric coupons, than from wiped coupons. However, there was significantly less off-gassing from coupons that were immersed with ACF fabric than with PolyClean fabric.

It also was shown that diffusion cleaning reduced the level of off-gassing from commercial gas sensors (Industrial Scientific T 80 single gas detectors) deliberately contaminated to a surface contamination level greater than 10 g/m² with diethyl methyl phosphonate, to a vapor concentration of less than 10-2 mg/m³, a value which is lower than the IDLH levels for Agents HD and GD.

The amount of off-gassing of DEMP from activated carbon fabric is one to two orders of magnitude smaller than from a non-adsorptive polyester fabric, PerfectClean, under otherwise comparable conditions. It was shown that the concentration of DEMP in a nitrogen stream flowing past a contaminated activated carbon fabric wipe increases as the concentration of DEMP in the fabric increases.

1. It was below 0.025 mg/m³, the estimated detection limit a the time of testing at an initial DEMP loading of 1 wt-percent of the activated carbon fabric from the onset of the off-gassing test;
2. It approached the detection limit after passing 60 L of nitrogen (flowing at 1 L/min) over a test sample that initially contained 3 wt-percent DEMP.

Conclusions:

1. The decontamination effectiveness of a decontamination wiper depends on the nature and characteristics of the substrate being decontaminated.
2. Wipers are a very effective means of removing surface contamination from impermeable, non-porous, and non-absorbent solid surfaces (i.e., metals, glass, nylon) where the contaminant remains on the surface. As the substrate becomes more permeable, more porous, and more absorbent, wiping effectiveness decreases as the amount of contaminant migrating into the sub-surface solid structure increases. While a wiper will remove residual surface contamination from polycarbonate or from surfaces painted with a chemical agent resistant coating, it will have little effect on contamination that has migrated below the surface, or has reacted with or dissolved in the substrate.
3. While attaining the high levels of decontamination required to allow equipment to be reused safely may not be achievable with a solvent wetted activated carbon wiper, this goal is attainable by a process that uses the same tools as wiping, but in a different way, and which ESI has called diffusion cleaning.
4. Diffusion cleaning can decontaminate complex electronic equipment to below the IDLH vapor off-gassing levels specified for chemical warfare agents, such as Agent HD or Agent GD.
5. The amount of off-gassing of DEMP from activated carbon fabric is one to two orders of magnitude smaller than from a non-adsorptive polyester fabric, PerfectClean, under comparable conditions.
6. Activated carbon fabric wipes can effectively pick up (over 95% surface removal) an aqueous biocide until they contain about twice their weight in absorbed liquid.

Supplemental Keywords:

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