Photo By David F. Peterson
Our team recognized the importance of consistently applying environmental sampling procedures at every hazardous material incident. This realization came after several years of being inconsistent whereby many responses utilized poor choices of monitors or in some cases no sampling efforts whatsoever. Inconsistencies were magnified shift to shift as we were all over the board with our sampling procedures. While there were no close calls (as far as we know), hindsight revealed that we were in need of some improvement, not just to be safe but also to be compliant with hazmat response regulations.
We knew what we had to do. We went to seminars and courses, we made phone calls to monitoring instrument manufacturers, and we discussed safety guidelines concerning our sampling procedures among ourselves. As a result of these efforts, we devised guidelines that will be used at each incident along with appropriate personal protective equipment. Multiple entries may be required to complete the procedure. They are as follows:
Environmental Sampling Procedure
- Step #1 - Check atmosphere for pH using both wet and dry paper.
- Step #2 - Check atmosphere for LEL and oxygen level simultaneously and with each of the following steps. Also, check for radiation on Step #2.
- Step #3 - Check toxic levels with available instrument(s).
- Step #4 - Check atmosphere with colorimetric tube(s) for known or unknown material(s).
- Step #5 - Use PID if CGI does not register to look for smaller concentrations.
- Step #6 - Use APD 2000 or SAW Minicad if nerve, mustard agents, tear gas, or pepper spray are suspected. Consider using nerve agent/blister agent monitors on Step #2, depending on circumstances.
- Step #7 - Use Miran SapphIRe, SensIR, HazMat ID, HazCat System, Chemical Classifier Strips, or other instrument(s) as needed.
Reasoning and Justifications
Step #1 - Many monitoring instruments use sensors that can be easily damaged by highly corrosive or caustic environments, especially by enduring chronic exposures. Manufacturers have stated that corrosive environments that cannot be endured by unprotected humans can also damage sensors. Since sensors are expensive, it behooves responders to avoid environments that significantly shorten their lives. Our guidelines simply use wet and dry pH paper upon initial entry. If either paper indicates dark red (acidic) or dark blue (caustic) environments, we may immediately exit and rethink subsequent entries with expensive instruments. Quantitatively, environments below pH of 3 or above pH of 11 should be reported to team officials in the cold zone. An alternative response to extreme pH environments may be to ventilate the area remotely. If there is no change in the pH paper, proceed to the next step. (Other colorimetric paper such as the Chemical Classifier Strips may also be used on Step #1).
Step #2 - It is crucial to sample environments that can ignite or combust simultaneously with the oxygen levels. Since combustible gas indicators (CGI) need sufficient oxygen to oxidize a sample, adequate oxygen levels have to exist in the sampled environment. CGI's also sample environments on a percent basis, and, since 1 percent equals 10,000 parts per million (ppm), a material will not combust until there is a large amount present. So, this step is measuring not only flammability and oxygen content, but also large amounts of an airborne material. Absence of a reading on a CGI does not necessarily indicate the environment is hazard free. A toxic hazard that the CGI could not detect may exist. We also use a radiation detector on Step #2 as a precaution to rule out the presence of radiation early in a response.
Step #3 - Many monitoring instruments today are manufactured with sensors that detect flammability, oxygen, and the toxic gases hydrogen sulfide and carbon monoxide all in the same instrument. These combination instruments are required by the OSHA permit-required confined-space regulation (29 CFR 1910.146). For many instruments, Step 3 can be achieved at the same time as Step 2. Other instruments can be utilized individually to check for specific toxic gases, but sampling should always be conducted along with a CGI and oxygen sensor for safety.
Step #4 - Colorimetric tubes can be used if the environment is known and the needed tube is available. Each tube can be read to determine the amount of the gas in the environment. Similarly, new chip system detectors can also be used as colorimetrics. If the environment is unknown, several manufacturers offer a tube system by which several tubes can be used at the same time to categorize an environment. A positive result may indicate the classification of the gas/vapor in the environment.
Step #5 - A PID (photoionization detector) can be utilized to quantify an environment after the material is identified. PID's can also verify concentrations found with colorimetric tubes or can be relied upon solely to find environmental concentrations. PID's should always be accompanied by CGI's and oxygen sensors for safety and because PID's commonly do not measure more than 1 percent or 10,000 ppm. It is important to remember that PID's measure small concentrations of an airborne hazard that are in the toxic range rather than the flammable range.
Step #6 - Depending on circumstances, sampling efforts may utilize both radiation detectors and/or weapons of mass destruction (WMD) agent detectors early in the procedure. A precaution with these detectors is that they may not be intrinsically safe, so they should not be used until Step #2. If they are accompanied by a CGI with an oxygen sensor, and a flammable environment can be ruled out, these detectors may prove to be invaluable. As a result of the terrorism and "dirty bomb" threat, many hazmat response teams are currently screening every incident for radiation.
Step #7 - Use other expensive and intricate instruments as needed. This step may include the use of infrared devices although some teams have adopted guidelines that bring the sample to the instrument instead of taking a bulky and intricate operating device into the hot zone. This type of thinking also works well with the wet chemistry type of identification kits that also utilize open flames in their processes. Finally, some teams also use vacuum canisters that can capture a gas or vapor in the release area and then be analyzed at a later time at a laboratory.
Practical Use
These steps should be utilized on the initial entry to categorize an atmosphere to protect not only personnel but the instruments themselves. Subsequential entries may find only selected instruments being used depending on initial findings or further environmental quantifying or qualifying. Paramount findings on the first entry would rule out excessively dangerous pH levels, flammable environments, and the presence of radiation. Entry personnel can then focus on the toxic hazard by identifying the hazard and its airborne concentration.
We have used a small plastic bucket with a metal handle to sample environments with this procedure. All of the initial entry environmental samplers fit nicely into the bucket. Upon entry in the hot zone or release area, one entry person would conduct the sampling with each step's equipment while the other entry person holds back with the sampling bucket while still maintaining close contact. The bucket person radios sampling results to team officials in the cold zone.
Conclusion
By using the environmental sampling procedure outlined at every incident personnel safety is enhanced, the team is consistent from shift to shift; and the lifespan of each monitoring instrument and its sensors are increased. Screening in this fashion also efficiently characterizes every environment and decreases the team's liability by assuring all hazards are revealed. The procedure is flexible, in that each step should be followed at every incident yet specific monitoring depending on circumstances can be employed. The procedure is also reasonable and prudent and easily employed. Think it through, and devise your own environmental sampling guidelines. Ultimately, you will decide if they improve your hazmat response program.
Any and all comments are appreciated! Please e-mail the author at [email protected].
