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Proving the Negative and Cleaned Sites

Proving the Negative and Cleaned Sites

Proving the Negative and Cleaned Sites:Alternate Approaches to Dealing with the Problem

Decommissioned Laboratory. Image: University of Vermont.

There is no more challenging mission in CBRN Operations than trying to prove something suspected did not occur at a location. This was most visible during the post-2003 period of the Iraq Survey Group’s examination of the Iraqi program (Duelfer 2009). It is extraordinarily hard to find evidence of CBRN activity at sites where chemical, biological, or even radiological work occurred, if those sites are cleaned, destroyed, or turned over to commercial use, prior to the operation. This is the same problem faced by IAEA and OPCW inspectors. 

Human intelligence may be the most useful in determining past use, but as was seen in Iraq, it may also prove highly unreliable. Many CBRN operations in "cleaned site" scenarios offers few alternatives to pure dumb luck. In order to improve the odds, several tactics can prove useful for collectors. Key is the ability to “target” any sampling to increase the likelihood of obtaining the “money sample.” There are two approaches to locating potential sample locations at “clean sites" involving chemical or biological work, which increase the odds of success. 

First, sample collection can be targeted using portable forensic light sources. The use of alternative light sources, or ALS, in criminal forensic work is long established. Recent advances in technology have developed portable versions that do not require external power. Operating within narrow bandwidths of light, the 450 nm (blue) being the most effective, these sources can prove invaluable in examining areas were contamination may not otherwise be visible or detectable by other means.

The first use of ALS is in sampling biological material. This is straightforward and mirrors their use in criminal forensics. ALS will fluoresce a variety of biological media and contaminants in the 450 nm range. The only drawback is that the lights do not distinguish one sample from another. A stain on a rug could be biological contamination from a lab, or it could be vomit. However, the use of ALS does improve the odds of getting something to sample rather than random or grid sampling in hope of hitting the right spots through chance.

ALS lights are also good at visualizing decontamination. Many dried decontaminate solutions fluoresce well under ALS, and evidence of poor decontamination is readily visible using these sources. This allows an operator to see any spots missed during in an attempt to decontaminate a surface or object. Sloppy or hurried decon can leave behind quite a bit.

Sloppy decontamination of Agar on glass using a rag dampened with Bleach and Lysol, as viewed under ALS light. Source: Author.

Another method of improving sampling odds at “clean” sites is the use of highly sensitive photo-ionization detectors that can detect at the parts per billion levels. By removing the filters, these point detectors become extraordinarily sensitive to Volatile Organic Compounds (VOC’s) within the Ionization Potential of their lamps. Again, these will not identify one sample from another, so cleaning products and chemical contamination of interest will look the same to one of these sensors, however, they can increase the odds of sampling something, rather than nothing. Alternately, some IMS detectors or other point detection devices may be used. These systems have their own drawbacks, but may be useful in certain circumstances, or if modified for more broad detection and analytical capabilities than standard commercial off the shelf versions.

For radiological and nuclear missions, detection for sampling is significantly easier at cleaned sites. Using standard detection equipment and working slowly and methodically, any radioactive contamination is certain to be found. Key to these operations is detector calibration and sensitivity, as well as the patience of the operator. The real problem is finding something of out of place in an area where there is supposed to be radioactivity, for instance a research reactor. Uncovering the use of one of these facilities outside of their original purpose is a difficult challenge and more of an intelligence collection and monitoring issue than one of actual sampling or CBRN operations. The human factors matter more in such operations than any physical evidence. Expertise again matters in these sorts of operations, especially when it comes to discovering anything "out of place." Turning on a radiation detector next to an operating research reactor will tell the operator nothing they didn't know already. That said, an experienced operator, trained in such missions, can uncover some amazing things, as the IAEA found out in Iran, when a wipe sample of a supposed decommissioned hotcell at a research facility turned up high-enriched uranium (HEU).

Beyond clean sites, there are the usual sample points associated with industrial and lab scale targets, filters, drains, ac units, hoods, etc. However, these typically provide verification only of current activity at a facility once changed to commercial  non-CBRN, production. Again, the knowledge and expertise of the collector and the analyst are vital, and the right experts are essential to increasing the likelihood of detecting process abnormalities or other things “out of place” with a facilities stated purpose. 

In the end, proving the negative is neigh impossible. However, for those sites that appear cleaned, or sites that may have turned over to other uses, there are means that offer potential for discovering such activity, and obtaining samples that might demonstrate previous CBRN activity, even if they can't preclude it. Because there are no full proof means of proving that something has not occurred at a site, there simply is no way to verify the negative, but by focusing on attempting to prove the positive (something DID occur) collection at these sites can still prove productive.

These sites are the least resource intensive, and usually require little in the way of PPE, unless there is suspicion of significant contamination. Gloves, boot covers, and an available mask work for most of these. They do require both time and significant sampling material, due to the nature of the site and the requirement to gather extensive samples with few clues as to where to sample. Vents, especially return air vents, filters, windowsills, and other areas, are all good places to start however. Narrowing down where to sample using technology like ALS or highly sensitive photo-ionization detectors may also be useful.  Time spent is critical at these sites, there is very little of use gathered from these sites without extensive sampling.


Duelfer, Charles. 2009. Hide and Seek: The Search for Truth in Iraq. New York: Public Affairs.

Drielak, Steven C. 2004. Hot Zone Forensics: Chemical, Biological, and Radiological Evidence Collection. Springfield, IL: Charles C. Thomas.

Patent Application US7186990


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