Unstable Chemical Controlled Safely
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The value of learning the nature of specific hazardous chemicals stored at a manufacturing site—before an emergency incident occurs—was once again demonstrated. Called to a large plant that produces plastic lenses for the eyeglass industry, the Fort Lauderdale, Fla., Fire Department found smoking cartons of diisopropyl peroxydicarbonate being thrown into a small lake on the plant property last Feb. 23.
The material is stored in plastic containers in 10-pound blocks and kept at 70 degrees below zero in electric freezers. But a preheater on the lid of freezer 1 malfunctioned and burned the rubber insulation away from the lid. When outside air then entered, the temperature started up and the contents started decomposing.
The smoking chemical was not removed from the plastic containers when they were taken out. Five of the packages sank in the lake. These caused no further problems, but two floated on the surface and continued to give off invisible fumes which affected eyes and throats.
Thought under control
Inside, other decomposing blocks had been removed from the defective freezer and placed in another unit maintaining the required temperature of —70 degrees. Plant personnel indicated that the situation was under control, and the other fire department personnel left.
I was on the scene for about 15 additional minutes when a plant worker came running from the blockhouse and stated that the temperature in the second chest had started a rapid rise, gaining 20 degrees in 15 minutes.
I recalled the companies to the scene and ordered Captain Janson to start an evacuation of a two-block area north of the blockhouse because this building isdesigned to explode outward in that direction. The police department assisted in the evacuation.
Engine 2 was ordered to stretch two 2 ½-inch supply lines to a deluge gun set up at the front of the blockhouse. When the lines were in place, a long wait began.
At this time, Captain Robson and Lieutenant Remer were on the phone to CHEMTREC trying to get additional information on the proper course of action to take. CHEMTREC did not have any new information, but they did put us in contact with Gary Gardner in Barberton, who is the plant chemist where this material is being manufactured. Gardner told us not to try to move any of the smoking material because this was very dangerous. (This, of course, had already been done earlier by the plant personnel.) Gardner told us that if the remaining material had not reached the critical stage (which is somewhere around zero or slightly above), decomposition could be reversed with the addition of dry ice.
As soon as a source of dry ice was found, at a local dairy, Engine 9S made an emergency run to get a good supply. Meanwhile, plant workers wanted to dump the entire contents of the second chest—30 cartons—into the lake. Not knowing what the consequences would be (the first few without any reaction could have been just luck) and being concerned about environmental damage, we took time to discuss this further.
It was agreed that we would move most of the decomposing containers to a third freezer. When all men had protective gear ready, including SCBA, six of the blocks in the worst condition were removed from their cartons and sunk in the lake. The rest were moved to the new chest—until it also started to heat.
Dry Ice helps
We feared we may have had an unstoppable reaction underway, so everyone wfts pulled back to the command post to wait on the dry ice. When it arrived, the temperature of the third chest was up to 20 degrees below zero—still in the safety zone but well above normal. One hundred and fifty pounds of dry ice were added to the top of the chest. All personnel pulled back again to wait.
The temperature continued to rise for 15 minutes, stabilized for 20 minutes and then started to drop. When the thermometer showed a drop to 50 degrees below zero, the material was turned back to plant personnel. The incident was under control 5½ hours after it began.
For next time
The following information should be helpful in the event of another incident. Getting past the chemical name is half the battle. There are three chemical names, all taken from the base chemical peroxidicarbonate:
- Diisopropyl peroxydicarbonate (IPP)
- Di-n-propyl peroxydicarbonate (NPP)
- Di-sec-butyl peroxydicarbonate (SBP)
All three chemicals have to be stored and shipped under refrigeration, at temperatures well below 0°F. IPP, shipped as a solid, melts at 46 to 50 degrees, and rapid decomposition occurs at 57 to 64 degrees. NPP and SBP, shipped as liquids, likewise decompose in this same temperature range.
If allowed to reach rapid decomposition temperatures, peroxydicarbonate gives off heat and flammable vapors. These vapors can easily catch fire from an ignition source or even ignite spontaneously from the heat generated by decomposition. If this heat is not removed, the decomposition becomes self-accelerating. Decomposition vapors are white or colorless until they catch fire. Keep ignition sources away.
Keep the material clean. Peroxydicarbonates are powerful oxidizers. Contamination by other chemicals, metals, dust or dirt can cause the material to decompose and give off flammable vapors.
If refrigeration fails, monitor the storage area holding pure peroxydicarbonate material and solutions visually, as well as with a high-temperature contact alarm set to give a warning signal well below the safe upper limit. Use dry ice to keep stored material cold. Place the dry ice above the peroxydicarbonate, not below it. If dry ice is not available, promptly dispose of the material.
Disposal
When using IPP, NPP or SBP, keep a container of sand or inert material such as vermiculite in the work area. Cover small spills with sand and dispose of the material immediately by taking it in a clean, open container to a wellventilated area free of any combustible material. Scatter the contaminated sand on the ground and allow the peroxydicarbonate to decompose gradually.
A large quantity of waste IPP, NPP or SBP can be disposed of by scattering it on the ground in an open, well-ventilated area free of ignition sources and combustible materials.
However, based on the experience at our incident with the two floating containers and the amount of eye irritating fumes given off, caution should be used in spreading a large amount anywhere near a residential area. The fumes from 30 or more containers would cause a serious problem. It would be prudent to pack the material in dry ice and remove to a remote area for dispersal.
Don’t fight the fire
In case of fire, leave the area as fast as you can. Don’t try to fight a peroxydicarbonate fire. Let it burn itself out. Limit the fire by spraying water from a safe distance to cool surrounding buildings and equipment. If the peroxydicarbonate storage units are not involved in fire, spray them with water from a safe distance. Don’t spray peroxydicarbonate trays or bottles directly. Don’t start cleanup and salvage operations until the area has cooled down completely.
Remember: A fire may lead to an explosion. Keep a safe distance from a fire. A distance of 2500 feet is recommended as a safe initial distance.
Any of the situations described that permits peroxydicarbonate material to decompose could also cause an explosion. This is the reason: If the vapors formed by decomposition cannot readily escape, they will build up pressure and burst the walls of a container. Storage containers of all types (bottles, catalyst charge vessels, storage tanks or buildings) should permit ready release of vapors resulting from decomposition.
Peroxydicarbonates become more sensitive to impact as temperatures increase. Tests made by the U.S. Bureau of Mines showed that certain severe conditions of impact plus confinement can cause explosive decomposition. Do not skid or drop peroxydicarbonates. IPP is not considered to be sensitive to friction, but you should avoid unusual conditions of friction such as grinding.
Consult a physician
These chemicals, both pure and in solutions, are extremely irritating to the skin and eyes. Adequate ventilation is necessary.
In case of contact with the skin, flush the contaminated area with water. Clean with soap and water and then with rubbing alcohol, if available. Take a shower. Remove contaminated clothing, let it hang out to air and launder before using again. Consult a physician. In case of contact with the eyes, flush them with water for at least 15 minutes, and consult a physician immediately.
For help in emergency situations with these chemicals, call PPG Industries plant at Barberton, Ohio, (216) 7534561. The chief chemist is Gary Gardner.
Gardner stated that there should be no chemical reaction if the chunks are immersed in a body of water, but they should be placed at different locations and not all dumped on top of each other. The material should break down into isopropyl alcohol and not harm the water. But dumping in water should be a last resort if all other efforts fail. Nor should the material be flushed into the sewer system.
Editor’s Note: According to the manufacturer, PPG Industries in Ohio, approximately 100 plants store large quantities of diisopropyl peroxydicarbonate for use in making plastic lenses for eyeglasses. The plants are mostly on the East and West Coasts.
