CHEMICAL DATA NOTEBOOK SERIES #113: ALLYL CHLORIDE
BY FRANK L. FIRE
Allyl chloride is a flammable, toxic, anesthetic, polymerizable, irritating, corrosive, colorless to straw-colored, volatile liquid with a garlic-like odor. It is used in the manufacture of insecticides, pharmaceuticals, resins, glycerine, allyl compounds, and other chemicals.
Allyl chloride has a flash point of -25°F, an explosive (flammable) range of from 2.9 to 11.2 percent in air, and an autoignition temperature of 737°F. Some references report the autoignition temperature as 905 °F; but when conflicting or differing values are given for hazardous properties, always adopt the more conservative value for emergency response purposes. Allyl chloride has a specific gravity of 0.94, a molecular weight of 76.5, and a vapor density of 2.64. It boils at 113°F, freezes at -210.1°F, and is slightly soluble in water. It may undergo hydrolysis in water, producing hydrogen chloride, a hazardous reaction product. Allyl chloride`s chemical formula is C3H5Cl.
Extreme flammability is allyl chloride`s major hazard. Ordinarily, the flammability of a liquid does not need to be qualified with an adjective, since the definition of a flammable liquid is a liquid with a flash point below 100°F. Allyl chloride certainly fits that description. However, its flash point of -25°F is so low that it will generate vapors sufficient to form an ignitable mixture with the air near the surface of the liquid or the container at almost all ambient temperatures found in the United States. Its ignition temperature of 737°F is easily reachable by all common ignition sources. Therefore, any time allyl chloride vapors are within the explosive (flammable) range, ignition (and explosion) is imminent. Its explosive range is sufficiently wide (8.3 percent) that it will be difficult to find a situation surrounding a leak or release where the vapors of allyl chloride will be in a too-rich condition (above the upper explosive limit, or UEL).
The range of concentration of product in air in which an ignitable mixture is formed is usually referred to as the explosive or flammable range. This range (designated as percent in air) usually is defined as the concentration of vapor or gas in air between the upper and lower explosive limits. However, when the vapors of a flammable or combustible liquid or a flammable gas are ignited, what occurs first is an explosion, however minor (and it usually is major). The term “flammable” no longer should be used to describe the range and its upper and lower limits since this term may lead you to believe that the major hazard of the product is its ability and propensity to burn. The real hazard, of course, is that the flammable liquid itself doesn`t burn–the vapors it produces burn and will explode violently on initial ignition.
Allyl chloride is a volatile liquid–it evaporates very rapidly, very quickly providing the fuel for an explosion. It boils at such a low temperature (113°F) that the implication is that it will generate tremendous amounts of explosive vapors in a very short exposure to the atmosphere. Therefore, allyl chloride will boil rapidly on exposure to an environment where the temperature is “normal” or 70°F (room temperature).
Its vapor density adds to allyl chloride`s explosion hazard. In addition, anyone without the proper respiratory protection exposed to the substance will be subjected to respiratory hazards. The vapors will “hang” together for a great distance (unless disturbed by the wind or some other dispersing factor), flowing downgrade and gathering in low spots in the terrain or in enclosed spaces. These vapor concentrations are extremely dangerous. They will almost certainly be within the explosive range and be above the levels that produce danger to human health.
A toxic material, allyl chloride will produce severe health hazards. Its TLV-TWA (threshold limit value-time weighted average) is one ppm (part per million of air) over an eight-hour period. Its STEL (short-term exposure limit) is two ppm over a 15-minute period. Symptoms of inhalation of a dangerous amount of allyl chloride include irritation of the upper respiratory tract, dizziness, eye irritation, headache, nausea, and eventual loss of consciousness. Depression of the central nervous system is common. Death can occur as a result of cardiac arrest or respiratory shutdown.
Ingesting allyl chloride will cause heart, kidney, and liver damage. All symptoms caused by vapor inhalation also might occur with ingestion of minor quantities.
If allyl chloride contacts the eyes, painful irritation, blistering, and deep-seated pain can occur. Skin contact will produce painful irritation and deep-seated pain as it is absorbed. Toxic quantities of allyl chloride may be absorbed through the skin.
Although considered a stable chemical, allyl chloride will react with certain chemicals such as acids; amines; active metals such as lithium, sodium, potassium, calcium, zinc, magnesium, and powdered aluminum; alkyls; metal halides; organic halides; and peroxides and other strong oxidizers. It also will react with ammonia, sodium hydroxide, benzene, and toluene, especially the latter two in the presence of certain metal halides and alkyls.
Allyl chloride is corrosive to certain plastics, rubber, and polymeric coatings. It will corrode carbon steel when wet with water and react with the galvanized coating (zinc) on steel. It is corrosive to human skin.
The combustion products of allyl chloride are hazardous. In addition to deadly carbon monoxide, the irritating gas hydrogen chloride is evolved.
Allyl chloride is a polymerizable substance, making it a monomer (a short-chained molecule that has the unique capability of reacting with itself to form polymers). The chemical reaction in which this occurs is called “polymerization,” a reaction that liberates tremendous quantities of heat. If the polymerization gets out of control or if allyl chloride is exposed to excessive energy in the form of heat or sunlight, a situation called “runaway polymerization” may occur. Under certain conditions, this reaction will transit to an explosion. There may be some debate as to whether the explosion would be a BLEVE (boiling-liquid, expanding-vapor explosion) or a runaway polymerization, but the result will be the same–disaster.
A spill of allyl chloride is a very serious event, and a release of any appreciable quantity must trigger the community`s emergency response plan as mandated by SARA (Superfund Amendments and Reauthorization Act of 1986) Title III. This action should mobilize the proper experts from every emergency response discipline. Allyl chloride is a flammable liquid, so initial approach and positioning of apparatus and equipment should follow the standard operating procedures established for such incidents. Approach from uphill and upwind, and immediately eliminate all possible ignition sources. Because of the extreme explosion hazard, evacuate a large area around the release and restrict personnel in the danger area to responders who are absolutely necessary to the safe handling of the incident.
Allyl chloride`s high volatility means it continuously will be generating tremendous amounts of explosive vapors quite rapidly. If the ambient temperature is anywhere above 0°F for any prolonged period of time, the ground and exposures will be approximately the same temperature–meaning that when a spill of allyl chloride contacts such a surface, it will generate large amounts of explosive vapors. Even if the ground is frozen, allyl chloride`s high vapor pressure will promote the evolution of high amounts of extremely dangerous vapor.
The spilled liquid will be evaporating quite rapidly, even as efforts are made to contain the spill, reduce the explosion hazard, and keep the contaminated area as small as possible. If a containment pond is constructed by pushing soil up around the area of the spill or a containment pit is dug to contain the liquid, use sparkproof and explosionproof tools and equipment. A containment pit is preferable when trying to contain allyl chloride or any other highly volatile liquid since the resulting surface area of the liquid will be less in a deeper pit than in a broad, flat containment pond. A good principle to remember is that the rate of evaporation for a liquid in two different vessels or containment areas exposed to the same atmosphere will be slower for the one with the smaller surface area, all other things being equal.
Anything that can slow the evolution of vapors will be helpful in reducing the immediate explosion and health risks. Applying firefighting foam may help, but it will have to be continually replenished as it breaks down. The volume of the containment pond or pit must be large enough to hold the increased volume of liquid created by the foam. The temperature of the applied foam also will cause increased evolution of vapor. Covering the surface of the spill with some compatible material will contain the vapor evolution somewhat.
If the surface of the liquid cannot be covered, prevent the dangerous accumulation of vapors. Since a good, strong breeze will disperse the vapors, hopefully to a concentration below the lower explosive limit, anything that moves them around should help to disperse them. Applying a high-pressure water spray or fog directly adjacent to the spill and in the path of moving vapors will help disperse them. When using this technique, be careful not to let the water contact the liquid. This will increase the volume in containment areas and cause the liquid to evaporate more rapidly and the product to spread over a larger area, since it will float on the water.
Spilled liquid that has been contained and is worth saving can be salvaged by pumping or suctioning it into secure containers, using sparkproof and explosionproof pumps and other equipment. Properly educated, trained, and equipped professionals should perform all salvage and cleanup activities. Fire service personnel and other emergency responders should not be involved in salvage or cleanup activities unless they have been educated, trained, and equipped to the same level as the professionals.
The environmental authorities will determine what and how much contaminated soil will have to be removed and disposed of in accordance with the proper federal, state, and local regulations. All incident commanders should pay close attention to the advice of these and other experts mobilized for the incident. After life and health considerations of the emergency responders and anyone else endangered during the incident, the environment now ranks next in importance, even above property. Fire departments and their leaders now are liable for any damage done to the environment during the handling of a hazardous-materials incident, such liability being mitigated if actions that caused environmental harm were carried out to save human life (but not property). Remember, whenever handling any incident, first, do no harm.
Prevent allyl chloride from entering a sewer system or waterway. As it enters the water, it will float on the surface, spread out, rapidly produce large amounts of explosive vapors, and slowly dissolve in the water. The vapors, including the possible presence of hydrogen chloride, will quickly fill the sewer pipe, and they will be forced upgrade and downgrade as newly evolved vapors push the old vapors away from the liquid. This will create serious explosion hazards at every point along the sewer where there is an opening to the atmosphere.
If the product enters a river or stream, it again will spread out on the surface of the water, slowly dissolve, and rapidly evaporate. Notify all downstream users of the water immediately because of the extreme explosion hazard that will be created if they should draw water into an industrial location to cool equipment. Environmental authorities must continuously monitor the water downstream to determine when it will once again be safe for use by industry and municipal drinking water systems.
Another hazard is present with every highly volatile, nonsoluble liquid with relatively high vapor densities that enters such a waterway. As the liquid evaporates rapidly, the vapors stay near the water`s surface, flow with it, and fill any channels between the banks of the river or stream. The presence of these vapors in areas where they are not expected will produce a highly dangerous explosion hazard all along the course of the waterway. The vapors may also be extremely hazardous to the health of all animal life in and near that waterway.
If the allyl chloride enters a pond or lake, once again a situation will exist wherein the product will spread out and float on the surface of the water, generating large volumes of explosive vapors that might be somewhat confined within the banks of the pond or small lake. Approach all bodies of water that have been contaminated with a highly volatile flammable liquid as you would any release of the liquid on land–very carefully.
In an incident involving a large release of allyl chloride or a rapid escape of vapors or liquid from a breached container, any fire that exists after initial ignition will involve combustibles remaining after the inevitable explosion. Allyl chloride is so volatile that any release will produce sufficient vapors to produce a large explosion, even if the ignition occurs a very short time after the release. Effective fire extinguishing agents include carbon dioxide, dry chemical, foam, and water. The overall effectiveness of any fire extinguishing agent (and therefore the overall effectiveness of any firefighting efforts) will depend on the type and quantity of fuel present, weather conditions, the terrain immediately surrounding the release, the quantity and type of fire extinguishing agents available to the firefighters, and the ability to deliver those agents properly.
Do not approach the ends of any tanks containing allyl chloride that have been heated or threatened by fire. If possible, do not approach those tanks or any containers from any direction, especially a container that has flame impinging on it. Do not extinguish escaping vapors that are burning unless the flow of fuel can be stopped immediately after extinguishment.
Although flammable liquids do not ordinarily BLEVE for several reasons, monomers, under certain conditions, will polymerize violently. This also means that the buildup of vapors inside the heated container may be so rapid that the container`s pressure-relief device cannot vent them to the atmosphere fast enough. In this case of overpressurization, if an impinging flame damages the integrity of the container, these two forces may produce a deadly explosion.
In any event, follow your training in fighting flammable liquid fires. Cool containers with water delivered by unmanned monitors positioned as far way as possible. Never get between containers of allyl chloride (or any other flammable or combustible liquid or compressed gas) and an approaching fire. If the leaking container is already burning and no life is threatened, you might allow the fire to burn itself out while you protect exposures.
PROTECTIVE CLOTHING AND EQUIPMENT
Choose protective clothing and equipment that will prevent allyl chloride from contacting the eyes and skin. Rubber gloves, aprons, and boots may offer some skin protection. Wear splashproof chemical goggles to protect the eyes. Don positive-pressure, self-contained breathing apparatus (SCBA) for respiratory protection. Consult the manufacturers of total encapsulating suits and allyl chloride for information concerning the degree of safety offered by the material used in the protective clothing.
Inhalation. Move the victim to fresh air and keep him calm and warm. If breathing has stopped or becomes labored, administer artificial respiration, being aware that such action might expose the first-aid giver to the material in the victim`s lungs or vomit. Seek immediate medical attention.
Eye contact. Flush the eyes immediately for at least 20 minutes, lifting the eyelids occasionally. Immediate medical attention is required.
Skin contact. Remove contaminated clothing carefully. Flush the affected body areas with large amounts of water. Medical attention is required for the irritation.
Ingestion. If the victim is conscious, make him drink two glasses of water immediately, and induce vomiting. Never try to make an unconscious person drink anything or vomit. Immediate medical attention is needed. n
FRANK L. FIRE is the vice president of marketing for Americhem Inc. in Cuyahoga Falls, Ohio. He?s an instructor of hazardous-materials chemistry at the University of Akron as well as an adjunct instructor of haz mats at the National Fire Academy. Fire is the author of The Common Sense Approach to Hazardous Materials and an accompanying study guide, Combustibility of Plastics, and Chemical Data Notebook: A User?s Manual, published by Fire Engineering Books. He is an editorial advisory board member of Fire Engineering.
IDENTIFICATION NUMBERS AND RATINGS
(Chemical Abstract Services)
(Standard Transportation Commodity Code)
(Registry of Toxic Effects of Chemical Substances)
(United Nations/North America)
(Chemical Hazard Response Information System)
(U.S. Department of Transportation)
NFPA 704 Rating
(National Fire Protection Association)
(International Maritime Organization)
3.1, flammable liquid