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Thursday
Apr222010

Anhydrous Ammonia

     Anhydrous Ammonia is the greatest hazard to Hazardous Materials Responders when on-site of a clandestine methamphetamine drug lab. The previous post outlined the assessment and identification of a “meth” lab and this post will examine the greatest challenge on one of these sites. Generally, the “homemade” containers for anhydrous ammonia are more durable than milk cartons and beer bottles, which end up holding the other contaminants. Once the open containers of fuel, iodine, acids and bases have been secured and isolated, the tougher problem of anhydrous ammonia can be explored. Most anhydrous ammonia is stolen from farm cooperatives by way of portable containers. On-site, “illegal” anhydrous containers vary from geographic area to area, ranging from beer coolers to propane cylinders as well as pop fountain cylinders. Regardless, the handling technique for a hazardous material responder yields two {2} basic options.

     Anhydrous Ammonia is a liquifacted gas cooled and compressed into a liquid state, both for use and shipment across the country. Its legal uses range from cooling fluid and fertilizer, to explosive production on mining sites. It is a colorless liquid when cooled and compressed, which exhibits a reflective sheen much like acetone in a clear clean vessel. When a container is opened and exposed to the atmosphere, in a few seconds the “headspace” above the product will begin to heat higher than the anhydrous ammonia boiling point. When this happens, you will begin to see the clear, sheening, liquid begin to boil. Instantly, off-gassing will begin and if not controlled, an evacuation will result. Ammonia is very caustic to the respiratory tract and one nose full is all that is necessary to drive you away from the area, quickly. When a large volume of Anhydrous Ammonia is released such as in a railcar spill, the vaporization and contamination is quick, covers a large area, contaminates the environment and makes “containment” improbable. On the site of a “meth” lab, we generally mitigate less than 20 lbs of this product.

     The volume of product in a container that one responder can carry is another matter altogether. Because of the inhalation hazard of this material, lab “cooks” keep their homemade containers sealed so that they too can operate within the confines of a laboratory. This is a blessing for hazardous materials responders, as even though the container is suspect, the contaminant is relatively confined for the moment. When a hazardous chemical is in an illegal container, it cannot be shipped. Even if transfer into a proper shipping container could be completed, the purity of the anhydrous ammonia could not be validated for re-use. In the field transfers are impractical, so the alternate solution is to change the nature of the contaminant rendering it less toxic. Once the volatility is reduced it can be safely transferred into the appropriate waste container.

     Such is the nature of Anhydrous Ammonia. 1] The first option in the field employs a technique called “Sparging”. Here we mix the contaminant, with a benign chemical {in this case water} rendering it less toxic. By blending, we yield Ammonium Hydroxide. The resulting chemical is very close to a very strong blend of ammonia cleaning solution. Once this has been accomplished, the ammonium hydroxide can be pumped into drums or totes, and safely shipped to an appropriate wastewater treatment plant. Major water treatment plants in metropolitan cities may even allow wash-downs into local waste sewerage systems. Since anhydrous vapors are very toxic, the anhydrous ammonia vessel must be opened and allowed to mix, underwater. This is accomplished by filling a drum with water, inverting the anhydrous container, lowering it into and under the water, and then slowly opening the vessel. You will experience a rise in the water temperature of the drum along with a rumbling sound as the anhydrous mixes with the water. This is proper and of no concern, as this reaction demonstrates that it is “going to completion”. Option 2], if the tank is a larger size and cannot be submerged, or for other reasons cannot be handled safely, fire apparatus with attack hand-lines will be needed on scene. Here, Stretch a hand-line towards the container and position it upwind from the containers vent orifice. Next, have a responder open the valve and vent the anhydrous gas to the atmosphere. Discharge the hand-line and spray down the vapors. The result is liquid ammonium hydroxide fertilizer "leachating" into the soil. At worst, the area of release will have a healthy lawn all summer long. Be sure to occasionally soak the venting orifice, as the attack-line water will prevent the orifice from freezing shut. Compressed gases cool piping when released rapidly from the pressure reduction caused as the “liqui-facted” anhydrous ammonia expands into the atmosphere. Two points of notice here, 1] this will take a longer time to accomplish than a “sparge”, as this material expands greater in air allowing for only a small “cracking’ of the discharge valve, than a full open mode afforded by a water matrix. Because of the great air expansion ratio, you will need a low release rate to be sure to soak all the vapors. 2] You will probably need a supply line for your Engine due to the limiting volume of a booster tank. If hydrants are not available, call for a water tanker before you begin.

                                                                                    Haz Mat Mike  

                                                                

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