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NOTE: This document is provided for historical purposes only.
The conduct of the decontamination of CBRN agents or toxic industrial chemicals (TIC) requires a trained responder properly wearing PPE and a trained decontamination team properly processing and operating together as one synergistic group to reduce the amount of contamination to a neglible defined level and prevent the spread of cross contamination. Vapor and liquid administrative and technical control lines delineate concentration zones applicable to areas of the decontamination corridor operations.
Practice and more practice does make near-perfect for a decontamination team. Proper use of mission specific protective ensembles coupled with best practice field expedient closure techniques for the neck, wrists, ankles, and respirator faceblank seal areas and good respirator wear discipline contribute to the overall protective posture of a responder.
Historically, the greatest technology challenge to protection was the ability to bridge the protective ensemble hood to respirator faceblank gap. "Leaks" commonly found in the field vary by the type of protective posture worn. Leaks are rare in a Level A posture unless there is a fair-wear-and tear abrassion or damaged caused by a foreign object. If a level A protective posture is compromised, the type of respirator being worn by the responder becomes the next improtant level of protection for the wearer followed by the type of protective dermal undergarment being worn. In all cases, NIOSH-approved respirators offering CBRN protection are expected to provide the greatest level of respiratory protection to a responder tasked to operate in Level A, B, or C. Typically, Level B or C protective postures may exhibit leak areas at the chest, zipper, wrist, and respirator-to-hood interfaces. Protective boots can collect decontamination solution run off. Protective gloves over time, collect human sweat, as does the interior of the respirator chin cup. Responders in protective posture routinely fine ways to open and close/reclose protective suits to allow wrists, foreheads, and necks to "Breath".
Decontamination to a determined efficacy level is agent specific and thus decontamination agent specific. Water still serves as the universal decontaminate. "How clean is clean?" is still the common unanswered question posed by emergency responders. The level of decontamination solution penetration to user dermal surfaces may or may not have a direct relation to the efficay of the decontamination solution to neutralize, remove, or coat the contaminant and prevent exposure. Responders can be contaminated but not exposed if PPE is properly donned in advance, responders are acclimitized to the level of PPE in advance, and the doffing process is conducted by two-man decon station members overseen by a technical specialist. Typically, JLIST and BDO overgarments are rolled inside-out and pulled away from the wearer when being removed from the contaminated soldier. Cross contamination is more prevalent if there is only one decon station worker rather than two. Detection methods must be used to determine the efficacy of the decontamination method before the inner layer of clothing or respirator is doffed. Wearers exhibiting levels of contamination above the negilble level must be rerouted to an additional decontamination corridor for further decon.
In my years as a nuclear, biological, and chemical (NBC) decontamination and reconnaissance platton leader, armored cavalry squadron chemical officer, infantry air assault brigade chemical officer, infantry division NBC Element director, corps artillery chemical officer and Airborne corps NBC Cell director, decontamination of persistently contaminated soldiers is time intensive, logistically draining, and disruptive to the operational tempo of a military combat unit. Combat operations routinely required joint forces to don and doff protective respirators and maintain a mission oriented protective posture (MOPP)Level 2 to 4 over time, conducive to the type of intelligence threat identified or presumed(SCUD Attack, Ammunition Supply Point Generated Downwind Hazard, adjacent unit GAS, GAS, GAS alarms, or direct indicators of agent contamination or residual effects). Therefore, military commanders traditionally abore doing decontamination training and actually see it as a rest period in training rather than a life saving experience. Individual decontamination, gross decontamination, and technical decontamination are the common emergency responder decontamination methods in use. They routinely incorporate standard top to bottom decontamination techniques coupled with deliberate sequential station applications resulting in complete removal of all external personal protective equipment, with the respirator being the last item doffed. Penetration of protective ensembles recognized as OSHA/EPA level B or C versus military specified protective overgarments merit correlation analysis to determine the quantity and relevancy of decon solution permeation and penetration per type of compliant ensemble.
The National Fire Protection Association (NFPA) has published consensus standards for protective ensembles offering Chemical/Biological protection. NIOSH recently published NIOSH Pub No. 2008-132 that provides guidance on NFPA compliant ensembles and the integration of NIOSH-approved respirators offering CBRN protection.
Response to Comment #1 (Cloonan). Thanks for your thoughtful and insightful comments. The authors have employed dirty doffing (aka contaminated doffing) evaluation in both laboratory and field settings. These techniques have been used with combinations of people and equipment that meet the standards of competency or have been subject to laboratory tests including MIST.
With respect to training and competency, vulnerabilities can be overlooked; our experience in field-based decontamination proficiency suggests that responders and receivers alike fail to appreciate just how vulnerable they can be during the decontamination and doffing process.
Dirty doffing evaluation provides feedback in the form of visible evidence that surface ensemble contaminants (simulated in this case) have crossed the protective barrier or not. When combined with process review and critique, participants themselves can suggest corrective actions that are specifically targeted to the people, procedures, or equipment involved in the decontamination process.
With respect to laboratory testing, the techniques represented in this poster have been applied with a number of JSLIST garments, both legacy and developmental, and "contaminated doffing" has already been incorporated in the ORD requirements for the design and acceptance of certain military protective ensembles.
Dirty doffing evaluation provides an opportunity to improve the overall performance of personal protective equipment by characterizing the overall effectiveness of the decontamination system (people, procedures, and equipment).
Thanks again for your comments. fnb
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