How Clean is Clean?: Assuring Decontamination Efforts are Adequate

Much has been written about hazardous materials decontamination over the years as far as who does it, where it is done, how it is done, why it is done, and when it is done. But, there is very little information or guidance pertaining to how to assure decontamination (decon) efforts are adequate. For the most part, when responders and/or victims complete their travel through the decon corridor an assumption is made that they are clean. But, is this value judgment safe? Can responders unequivocally and without reservation say that each and every person who has been deconned is clean? If you cannot answer "yes" to this question then you (your agency) have some work to do.

You may counter the question above by stating that your decon efforts of the past have been successful in that no post decon exposures or illnesses have occurred. Maybe, your track record shows an over-reliance on chance or even luck. OSHA, the federal agency who watches over hazmat response, realizes the importance of conducting decon efforts and assuring its effectiveness. Over the last 15 years several OSHA plan states have issued citations and fines to fire departments for lack of decon efforts, including assuring decon effectiveness. All of the citations are based on the Hazwoper law found in 29 CFR 1910.120 (q). Based on these legal requirements and personnel safety issues there is more than enough motivation to take the steps that assure effective decon efforts are employed, but how?


The old reliance on guesswork will simply not be defensible if cited by an OSHA representative or even if called to testify in court because of a lawsuit. A more defensible approach would be to develop documented methods of assuring decon effectiveness. Essentially, there are only two methods that can be utilized to determine if decon efforts are effective: qualitative and quantitative.

Qualitative methods to determine decon effectiveness involve making judgment decisions on whether all harmful contaminants have been removed from responders and victims and their clothing. This usually involves a visual inspection. Some agencies have applied colored syrup to responder's clothing before they undergo decon. This way the decon personnel can judge their efforts during the decon process by working to remove the syrup. Again, if no syrup can be seen after responders exit the decon corridor then the assumption is made that the responder is clean because any real contaminant was probably washed off along with the syrup.

Another visual method involves the employment of a fluorescent dye which is again applied to responder's clothing before the decon process. While most of the dye can be seen during the decon process and therefore removed, any dye that remains can be detected under an ultraviolet light. If contamination is left on a responder a UV lamp that shows bright yellow or greenish residue will alert decon workers that more decon efforts are needed. These dyes can be prepared by adding sodium fluoroscein salts to water or even by purchasing commercially prepared solutions. Still, the qualitative methods leave too much safety to guesswork. Just because all of the syrup or most of the fluorescent dye has been removed does this mean the actual hazardous material has been removed? Also, if some of the dye is detected under UV light how much residue is considered safe? Finally, would we really apply syrup or dye to victims in street clothes, especially if they are in need of medical attention? Merely asking these important questions make qualitative methods seem too subjective.

Quantitative methods that employ environmental sampling techniques can detect liquid and gas contaminants in small, numeric amounts to determine decon effectiveness. The instruments that would be needed would consist of a mix of expensive and elaborate and inexpensive and simple instruments. Employment of this technology would enable decon personnel to detect and measure contaminants and then decide a course of action. In the area of decontamination this would almost always neccessitate more decon efforts.

Generally, post decon air sampling of responders should consist of the use of photoionization detectors (PID) because of their low sensitivity. Since PID's can detect in the parts per million (ppm) and parts per billion (ppb) range, any results can be compared to acceptable exposure levels to determine a course of action. Decision makers, however, need to keep in mind the limitations of PID's in that a material's ionization potential needs to be known and the correct lamp selected. Also, the PID correction factor needs to be utilized for accuracy of measurements. All of this is only true if the contaminant can even be ionized. Other expensive instruments that employ electrochemical, metal oxide, or even infrared technology can also be utilized to detect contaminants.

Remember, too, that radiation detection instruments should also be employed in decon effectiveness determination, especially in these times of WMD risk. Colorimetric paper could be used to determine if acidic or basic material existed on responders after decon. There are several types of inexpensive colorimetric paper that will detect several other hazards in addition to pH. At any rate, quantitative methods are very objective when it comes to providing data for response actions. Quick personal scans with sensitive instruments seem reasonable and only take a few minutes to assure decon is effective.

How Clean is Clean?

Quantitative methods that utilize monitoring instruments may yield results that will necessitate additional decon efforts. Even though many results may require that responders return for additional decon efforts some results may allow the responder to exit. The answer as to which is which depends on the standard that is followed to make such determinations. One benchmark that could be considered for determining what levels are safe is the American Conference of Governmental Industrial Hygienists (ACGIH) annual publishing of their threshold limit values (TLV's). Standard Operating Guidelines (SOG's) for agencies that provide decon capabilities could employ the ACGIH data to determine decon effectiveness. For instance, if the contaminant is known and the selected monitoring instrument detects a level that exceeds the TLV-Time Weighted Average (TWA) then the responder needs to return to the decon corridor for additional decontamination. If a reading for the same contaminant is below the TLV-TWA then the responder may be allowed to pass through the decon corridor because the concentration level is below those that cause adverse health affects. If a contaminant is known and is listed as a carcinogen (C) by the ACGIH, and any level is detected, then the responder needs to return to the decon corridor. A zero tolerance should also be observed for all unknown contaminants as well as chemical and biological warfare agents based on their toxicity.

For radiological threats any readings that are greater than 100 counts per minute (CPM) over the ambient radiation levels should have responders return to the decon corridor. This Nuclear Regulatory Commission (NRC) recommendation can be found by using a pancake probe with an instrument that is calibrated in the CPM mode. For pH hazards, levels closer to 7 would be ideal and can easily be attained through wet decon efforts.

Decon Effectiveness Equipment

In order to decon responders and victims and assure they are safe and clean when they exit the decon corridor the following equipment may be helpful;

For victim decon:
  • soft brushes
  • nail brushes
  • wash cloths
  • and Q-tips

For monitoring:

  • PID's range from $3,000 to $6,000 each
  • Radiation detectors with pancake probe range from $2,000 to $3,000 each
  • WMD monitors range from $5,000 to $10,000 each
  • pH paper is approximately $15 per roll
  • Colorimetric strips or badges are approximately $8 to $25 each

Whether the above equipment is dedicated to the decon corridor for decon effectiveness evaluations or it is supplied by the monitoring division all personnel need to be adequately trained in the correct operation for each instrument and also how to interpret the data. Any and all data received from the monitors should be documented and passed on to major decision makers.


Writing and implementing decon effectiveness standard operating guidelines will assure decon efforts are safe and efficient. Practice them regularly and employ them at every incident. Then when anyone asks "are your decon efforts safe and effective?" you can answer without hesitation "most definitely!".

As always, any and all comments are welcome by emailing the author at