Anhydrous Ammonia Spill Day

It looks like someone declared June 8, 2007 to beScreening Threshold Quantity (STQ) listed in the
the day for serious Anhydrous Ammonia spills fromproposed Appendix A, Chemicals of Interest, to 6
refrigeration systems across the country. ThereCFR part 27. Cooling systems having more than 7,500
were three separate instances of significant spillspounds of Anhydrous Ammonia in the system would
reported today. Mount Sterling, KY, Wyalusing, PA,make that food processing company a ?Chemical
and Milwaukie, OR all had releases in the last 24Facility? under the rules of this regulation.
hours. No one was killed, but a number of peopleAccording to the EPA Risk Management Plan (RMP)
were taken to the hospital, businesses wereguidance documents, 7,500 lbs of Anhydrous
evacuated, and residents were told to shelter inAmmonia released in 10 minutes time from a
place.pressurized system (clearly a catastrophic leak, not a
There were explosions associated with two of thefaulty valve) will have a plume with a toxic end point
incidents. There are reports that the ammonia leak at3.2 miles down wind from the site of the leak (Table
a Nestle Plant in Kentucky caused an explosion that9, 1.5 m/s wind speed). That means that anyone
blew down a wall at that plant; no injuries from thebetween the leak and 3.2 miles downwind could be
explosion or falling debris have been reported. Theexposed to dangerous concentrations of Anhydrous
American Cold Storage facility in Oregon had anAmmonia.
unexplained (as yet) explosion result in the ammoniaRather obviously, from the lack of casualties, none of
leak. There were no reports of an explosionthese three release events came any where near
associated with the leak at Cargill Taylor Beef Plant in7,500 lbs in 10 minute release rate required for a 3.2
Pennsylvania.mile long toxic plume. There is nothing in any of the
Anhydrous Ammonia is favored in many large coolingavailable article that tells anything about the release
systems because it has better heat transferrate for these accidents, but from the description
characteristics and is cheaper than the refrigerantthey did not seem to be catastrophic release events.
gasses used in home cooling systems andBut what about the explosion caused by the release
refrigerators. The problem is that this material is veryin Kentucky?
reactive and is classified as a Toxic by Inhalation gas.Anhydrous Ammonia is a very reactive chemical, and
Fortunately, the gas is extremely irritating at welleven by itself can form an explosive mixture when
below the toxic level so that when a minor leakmixed with air at concentrations of 16 to 25%
happens, unprotected people evacuate the areaAmmonia in air, though it would require a strong
quickly with little urging. A catastrophic leak, however,ignition source. It reacts to produce explosive
can overcome people before they have a chance toby-products when it mixes with Chlorine, Bromine or
get clear. This is partially because many people areIodine. Violent reactions occur with Bleach or
temporarily blinded by less than lethal concentrations.Peroxides. It also forms explosive compounds with
The food industry has long maintained that theyGold, Silver and Mercury. So, while explosions are not
should not have to comply with any handlingpart of the normal operating conditions of
restrictions on Anhydrous Ammonia required underrefrigeration systems using Anhydrous Ammonia as a
various Federal laws, since they don?t actually handlerefrigerant, an explosion after a significant leak would
Anhydrous Ammonia; it stays in a closed system.not be totally unexpected.
During the regulatory comment period theyJust maybe, DHS was correct in setting the STQ limit
complained about being required to submitfor Anhydrous Ammonia at a low enough level so
information under the new Chemical Facilitythat some refrigeration plant users could be labeled
Anti-terrorism standards based on the 7,500 poundas Chemical Facilities.