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Tuesday
Jan012013

Decontamination Techniques

The concept of decontamination must be based on the characteristics of the contaminant involved. The following ideas for consideration can maximize your system, personnel, and equipment, allowing for increased effectiveness and manpower while affording you the ability to stage and selectively respond to each scene with the proper decontamination tools as opposed to all the decontamination tools.

1] Is the contaminant of a nature that “HSR” concepts should be evaluated?

2] Is a full “wet-decon” line an effective use of manpower?

3] Could decontamination equipment be staged to “selectively” respond?

Decontamination (“High Static Risk”)

“High Static Risk” or HSR decontamination deals with the concept of not all hazardous materials being axiomatic in nature unless they exist in “high or obvious” concentrations. Many chemicals or contaminants are only a threat of contaminating unprotected personnel or the public inside or outside a hot zone area under high concentration conditions. Here the concept for the responder’s consideration is; can I minimize my decontamination system for the “site” based on the persistency and concentration volume of the hazard? This answer may be a resounding YES, if the identity, volume, and harmful persistency of the release can be determined. If a hazardous material that is carried by an “entry team” outside of the hot zone becomes by definition “not of sufficient quantity or capable of producing harm” your decontamination strategy can adapt to deal with a lesser hazard level.

The overall struggle with the assessment of this issue is the concept that site responders are responsible for determining exactly what is deemed “high” amounts. Some substances have a “high static risk”, some do not. Some examples of “high static risk” materials are;

1] Highly concentrated corrosives (vaporizing)

2] Asbestos (large crumbling amounts)

3] Cyanide salts and related nitrate compounds

4] Hydrogen cyanide gas

5] Hydrofluoric acid solutions

6] Mercaptans

7] Nitrogen containing oxidizers (and other oxidizers) which may produce anilines, aryl amines, aromatic nitrogen compounds, chlorates, etc.

8] Pesticides

9] PCB’s

10] Phenol and phenolics

11] Oily or adherent toxic dusts and liquids

12] High level radioactive material

The above list is not limited to these types of materials. Most of these “high” amounts are readily determinable. When concentrations reach the sensory limit of breaching the exclusion zone while maintaining aggressive toxicity detection by unprotected site personnel, these should be determined as amounts that have likely reached “High” risk levels. Examples include amounts that are readily seen or smelled from a distance registering the affect that “this contaminant is really thick!” While this by no means is a very scientific measure, it is easily observed by responders on the scene. Realize that each chemicals specificity must be evaluated for the “amount” that triggers “high risk” profiles.

Some examples of “low risk” materials are also included below;

1] Most gases and vapors that disperse upon release

2] Weak corrosives excluding hydrofluoric acid compounds

3] Arsine gas

4] Carbon monoxide gas

5] Phosphine gas

6] Smoke and combustion products

7] Small quantities of hydrocarbon solvents

8] Low level radioactive materials

The hazardous materials responder does have some parameters when analyzing “Risk Assessment” regarding this concept. He/she should be guided by the following articles and any additional that he/she may deem primary to delineate high risk from low risks.

1] The form of the substance (gas, liquid or solid)

2] Its ability to adhere to surfaces

3] The concentration or amount present

4] Type of surface contaminated (Skin, CPC, etc)

Selection Type Considerations

Your initial decontamination plan “before” identification should be based on the worst –case scenario until proven otherwise. This of course is assuming there is “the total absence” of identity information regarding the contaminant until after you analyze your collected data from a hot zone reconnaissance team. This decontamination plan can be evaluated with the above concepts and then reasonably and more accurately modified. Using this technique will allow the responder to eliminate unnecessary decontamination stations by adapting your “line” to the specific “site” and “contaminant.” This is accomplished by considering the following factors;

1] Type of contaminant

2] Amount of contamination

3] Type, level and PPE or CPC

4] Work function

5] Location of contamination and accessibility

6] Establishment of procedures

Methods of Decontamination

The methods of decontamination are wide and vary with the technologies involved to include new methods being developed. What is constant is the fact that many variables must be evaluated before a specific style is chosen. The ultimate goal should be concerned with safety and “workability” for the entry team as well as the overall operations ease and success. Decontamination is divided into two (2) broad categories, physical and chemical.

Physical methods usually concentrate on the “physical removal” of the contaminant from all objects involved. While some of the following methods may dilute the contaminants concentration, the contaminant still remains chemically unchanged.

1] Dilution

2] Brushing or scraping

3] Adsorption and Absorption

4] Removal and disposal

The end result of this type of decontamination is that the contaminant, while removed still exists in a form that must be remediated as hazardous waste. This means additional handling, cost, and danger to responders or civilians if spilled a second time during transport to a TSD (Treatment, Storage, and Disposal) facility.

Chemical methods while are generally more involved do have the added benefit of rendering the contaminant less harmful or harmless depending on the chosen method. Some of methods are listed below.

1] Chemical degradation

2] Neutralization

3] Solidification

4] Disinfection and sterilization

Dry Decontamination

With the advent of disposable CPC came the onset of a new concept in decontamination. “Dry” Decontamination became a technique to not only reduce the size and manpower requirements of a full scale 19 step EPA (Environmental Protection Agency) decontamination line, but also reduced drastically, the cross contamination seen traveling from station to station within common “Wet” decontamination lines. Also eliminated was the ailment of purchasing suits which have become outdated due to storage or infrequent use or, so contaminated that wet decontamination was ineffective. Through the use of “dry” decontamination, additional waste created from a full scale “wet” decontamination line is greatly reduced and in some cases, eliminated.

Another advantage of “Dry” decontamination has always been the question of decontaminating the decontamination equipment. How clean is clean? This idea has frustrated Decontamination Team Leaders for years. The thought of returning with contaminated equipment to your storage area or response vehicle and the subsequent “cross” contamination of clean equipment or areas is a nightmare scenario for responders. Once “Dry” decontamination was placed into service many of these worries have all but disappeared.

Below is a generic format for achieving “Dry” decontamination. A full description in detail is explained in my text, “Practical Haz-Mat.” Appreciate that when you adjust this procedure for your operations, the format will experience changes for each level of protection due to the structural ensemble’ of components and whether or not encapsulation is utilized.

1] Once responders return to the decontamination corridor, Entry team members should assist each other with any tape removal that was placed on them by “tenders” before the entry was made.

2] These materials are to be placed inside a plastic waste bag that each entrant will then step into. Place these bags close enough together so that each entry team member may assist with the unzipping of each other’s entry suit zipper.

3] Each entrant carefully removes his/her level "A" suit down to waist level. CAUTION; this must be done by only touching the outside of the suit with exterior gloves, thus reducing cross-contamination.

4] Once this step is completed, entrants remove outer boots and outer gloves placing them inside the waste bag they are standing in. Note: (If outer gloves and boots are disposable, you may eliminate step one (1)).

5] With their mid-line or inner gloves, remove the remaining level “A” by touching only the inside of the suit material allowing the “entrant” to step out of the contaminated CPC and into a second waste bag, towards the direction of the cold zone.

6] Once inside the second waste bag, deposit all remaining inner disposable equipment and step out into the cold zone while still breathing through respiratory equipment. In the “Cold Zone”, recharge, replace and or secure respiratory equipment for further decontamination based on your protocols.

Decontamination Area within the CRC (Contamination Reduction Corridor)

Having achieved this set-up, you will note that the CRC is significantly reduced. At this point your operation will be left with only two (2) bags/entrant of waste that can be sealed and removed with any other waste from the site by the contracting Environmental Waste removal company. The main point of contention is the probable contaminated CPC is transported to a TSD facility rather than returning to your uncontaminated facility. This process of “Dry” decontamination will reduce cross contamination while utilizing manpower for remediation techniques to better control the environmental hazard. In many cases when materials are easily identified this can at least enable your team to divide large amounts of decontamination gear into two (2) separate response vehicles, one for HSR and one for LSR materials. This can not only increase your response options for multiple incidents, but create a work site less littered with unessential equipment for responders to “sort through.”

                                      Haz Mat Mike

 

 

 

 

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