Handling Anhydrous Ammonia Emergencies

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Spring is just around the corner and anhydrous ammonia is being shipped to fertilizer companies for use during spring planting at farms around the country. The material is transported in cylinders, insulated and uninsulated tank cars, barges and tankers.

Anhydrous ammonia bulk-storage tanks are a common sight in many communities across rural America as well as in some urban areas. Anhydrous ammonia is stored in bulk in large-capacity containers installed above or below ground. Normal above-ground storage is in uninsulated pressure storage tanks. Very large above-ground storage containers are often low pressure, refrigerated and consequently insulated. Farmers will often transport anhydrous ammonia from fertilizer plants in trailer tanks hooked to pickup trucks or tractors. The material is not dangerous when handled properly, but if not handled carefully it can be extremely dangerous.

Prepare For The Worst

Efforts are made by shippers, end users and the fertilizer industry to transport, store and provide safe use of anhydrous ammonia. In spite of the safety measures, accidents can and do occur and emergency responders need to be prepared to deal with anhydrous ammonia emergencies. Accidents may range from releases that affect only responders to those that can affect an entire community. Accidents may also involve victims who have been splashed with ammonia. Therefore, planning and training must include emergency medical people as well as other responders.

  • On Jan. 18, 2002, a Canadian Pacific freight train derailed outside Minot, ND. Five of the cars carried anhydrous ammonia. Leaking ammonia killed one person and sent dozens of others to hospitals for treatment. Ten of those seeking treatment were admitted to the hospital. Some local residents were evacuated while others were asked to shelter in place. Civil Defense sirens and local radio and TV stations alerted residents.

  • In 1984, one firefighter was killed and a second was burned over 72% of his body in an anhydrous ammonia explosion and fire that occurred in Shreveport, LA. Ammonia was leaking inside a cold storage building. While firefighters were working inside in Level A chemical protection, the ammonia reached an ignition source. Though it is listed as a non-flammable gas by DOT, ammonia burns inside structures and confined spaces; it is less likely to ignite out in the open. Precautions should be taken for ammonia leaks inside buildings just as for any other flammable gas.

  • An accident occurred in the late 1990s in a cold storage building in Ortana, PA. Two plant maintenance workers, who were also local volunteer firefighters, were conducting routine maintenance on liquid ammonia lines within the facility. A leak occurred, the men were splashed with liquid ammonia and both died. Firefighting personnel responding to the incident were burned by ammonia vapors as they entered the facility in turnouts to rescue the workers.

  • In Delaware County, PA, in the early 1990s, an ammonia leak occurred as workers were removing the material from a cold storage building. The entire first-alarm assignment was exposed to ammonia vapors and experienced symptoms. They all had to go through decontamination and medical treatment at the scene.

Material's Dangers

Anhydrous ammonia is classified by the U.S. Department of Transportation (DOT) as a Class 2.2 Non-flammable Gas. Unfortunately, this classification leaves two important hazards of anhydrous ammonia unidentified by the DOT placarding and labeling system. Not only will anhydrous ammonia burn under certain conditions, it is classified as a caustic (corrosive) liquid and poison gas in other parts of the world. U.S. manufacturers identify the hazards as flammable, toxic and corrosive.

Photo by Robert Burke
Anhydrous ammonia is toxic, and inhalation of concentrated fumes may be fatal. Level A chemical protection is required when responding to ammonia leaks.

Anhydrous means "without water." Other chemicals also have the word anhydrous in their name and it means the same thing, without water. Anhydrous ammonia (NH3) is a colorless liquefied gas that is free of water; for that reason, it has a high affinity for water. Thirteen hundred gallons of ammonia vapor will dissolve in just one gallon of water. It has a very sharp, intensely irritating odor - anyone in the area of a release will not want to stay!

Ammonia gas is lighter than air and is easily liquefied by pressure. It has an auto ignition temperature of 1,204 degrees Fahrenheit and a flammable range of 16-25%. The reason the DOT does not consider ammonia a flammable gas is the definition used for flammable gases. According to the DOT, a flammable gas has a lower explosive limit (LEL) below 13 or a flammable range of greater than 12 percentage points. Ammonia misses the definition on both counts. Ammonia has a LEL of 16, three points above the DOT requirement for a flammable gas, and the flammable range is 10 percentage points, not the 12 required by the DOT's definition. It does, however, burn, and has injured and killed firefighters when it ignited. Anhydrous ammonia is toxic with a threshold limit value (TLV) of 25 ppm in air. Inhalation of concentrated fumes may be fatal.

Necessary Protection

Responders to incidents involving anhydrous ammonia will require Level A chemical protective clothing and self-contained breathing apparatus (SCBA) to protect them or to perform rescue. Anhydrous ammonia is also a very cold liquid, as it is released from a tank its temperature is -28F, and can cause serious thermal burns very quickly. There is no protective clothing to protect responders from the severe cold of the liquid. When released, the liquid ammonia quickly returns to the gas state at the expansion rate of 850 gallons of ammonia gas for every gallon of liquid.

Ammonia solutions that are available commercially for cleaning purposes contain anhydrous ammonia that has been dissolved in water. It still has a strong ammonia smell, but it is no longer flammable. Ammonia solutions remain corrosive and toxic, but by different routes of exposure and to a lesser degree. In higher concentrations ammonia solutions become the liquid corrosive ammonium hydroxide, which is used in the production of lye. Anhydrous ammonia's primary uses are as an agricultural fertilizer and refrigerant in cold storage facilities. It is the oldest material used as a refrigerant; but 80% of its use is as a fertilizer. Ammonia is also an ingredient in the manufacture of gunpowder and sulfuric acid as well as illegal methamphetamines.

Photo by Robert Burke
A railroad tank car carrying anhydrous ammonia, similar to the cars that derailed outside Minot, ND, in January. Such railroad tank cars may be painted black or white.

Theft of anhydrous ammonia for clandestine purposes has resulted in numerous leaks and injury and death to those stealing it. Valves have been left open, locks broken, and improper hoses and containers used in the illegal transfer. When placed in portable propane cylinders, the ammonia attacks the brass fittings and causes leaks. Stolen ammonia is transported in dangerous conditions, such as in the trunks of automobiles. This can present a dangerous situation in an accident for emergency responders. In March 2000, the EPA issued a Chemical Safety Alert for Anhydrous Ammonia Theft.

Mild exposure to anhydrous ammonia can cause irritation to eye, nose and lung tissues. When NH3 is mixed with moisture in the lungs, it causes severe irritation. Ammonium hydroxide is actually produced in the lungs. Prolonged breathing can cause suffocation. The human eye is a complex organ made up of nerves, veins and cells. The front of the human eye is covered by membranes, which resist exposure to dust and dirt. None of these can keep out anhydrous ammonia, because the entire eye is about 80% water. A shot of ammonia under pressure can cause extensive, almost immediate damage to the eye. The ammonia extracts the fluid and destroys eye cells and tissue in minutes.

If you get a shot of anhydrous ammonia in your eye, the first few seconds are crucial. Immediately flush the eyes with copious amounts of water. If wearing contact lenses, remove them. Eyes doused with ammonia close involuntarily, but they must be forced open so water can flush the entire eye surface and inner lining of the eyelids. Continue to flush the eyes for at least 15 minutes. Get professional medical help as soon as possible to prevent permanent damage. If water is not available, fruit juice or cool coffee can be used to flush the eyes. Remove contaminated clothing and thoroughly wash the skin.

Clothing frozen to skin by liquid ammonia can be loosed with liberal application of water. Wet clothing and body thoroughly, then remove the clothing. Leave burns exposed to the air and do not cover with clothing or dressings. Immediately after first-aid treatment with water, get the burn victim to a physician. Do not apply salves, ointments or oils-these cause ammonia to burn deeper. Let a physician determine the proper medical treatment. Remove the victim to an area free from fumes if an accident occurs.

Photo by Robert Burke
A farm tank containing anhydrous ammonia. Note the red emergency water tank on the top.

If a patient is overcome by ammonia fumes and stops breathing, get the person to fresh air and give artificial respiration. The patient should be placed in a reclining position with head and shoulders elevated. Basic life support should be administered if needed. Oxygen has been found useful in treating victims who have inhaled ammonia fumes. Administer 100% oxygen at atmospheric pressure. Any person who has been burned or overcome by ammonia should be placed under a physician's care as soon as possible. Begin irrigation with water immediately. The rescuer should use fresh water if possible.

If the incident is a farm accident, there is a requirement for water tanks for irrigation of the eyes and body on the anhydrous ammonia tank. Open water in the vicinity of an anhydrous ammonia leak may have picked up enough NH3 to be a caustic aqua ammonia solution. This could aggravate the damage if used in the eyes or for washing burns. The victim should be kept warm, especially to minimize shock. If the nose and throat are affected, irrigate them with water continuously for at least 15 minutes. Take care not to cause the victim to choke. If the patient can swallow, encourage drinking lots of some type of citrus drink such as lemonade or fruit juice. The acidity will counteract some of the affect of the anhydrous ammonia.

Emergency Response

Response to anhydrous ammonia emergencies can present many challenges to emergency responders. Ammonia is colorless, so there may be no visual indications of where the gas is. There are things to watch for. Ammonia gas will quickly turn vegetation brown. If it's a time of year where the vegetation is expected to be green, then look for brown vegetation. You can also watch for animal or bird kill, which may have resulted from exposure to the ammonia gas in a release. Ammonia also has a strong odor; you can smell it before reaching a lethal dose. However, as with all hazardous materials, responders should not be in a position to smell materials.

Photo by Robert Burke
A highway tanker truck transporting anhydrous ammonia.

Firefighter turnouts do not provide protection from ammonia gas or liquid, although SCBA will protect the respiratory system. Ammonia vapors will seek out locations on the bodies of responders where there is moisture. The eyes are a major concern as they can be damaged or blindness can occur from ammonia contact. Areas in the groin and armpits are also potential moisture spots. However, firefighters in full turnouts can sweat and moisture can be present on any part of the body, depending on ambient temperatures. First responders in firefighter turnouts should avoid contact with ammonia vapors or liquid.

Because of its great affinity to water, first responders can use hose streams to decontaminate victims exposed to ammonia vapors or liquid. They can also use fog streams to dissolve ammonia gas from the air to protect victims or those in harm's way. Remember, however, that water and ammonia form ammonium hydroxide, a corrosive liquid. After victims receive emergency decontamination, efforts should be made to control the runoff.

Anhydrous ammonia can cause corrosion on metals, particularly copper, brass or galvanized. Many parts of fire apparatus and equipment are made of brass, which can be damaged if in contact with anhydrous ammonia. Like anhydrous ammonia, liquid petroleum gas (LPG) is stored in the same type of steel tanks. However, the fittings on the LPG tanks are brass, while those on anhydrous ammonia are black iron. Black iron fittings are ferrous metal and can spark. Brass, made of copper and zinc, is nonferrous, and will not spark.

Anhydrous ammonia stored in a tank with brass safety and control valves will eventually cause them to corrode, so the valves fail or become inoperative. Anhydrous ammonia does not have this effect on black iron. In the past, some fertilizer dealers used anhydrous farm tanks in the winter for LPG. Farmers used the tanks to run grain dryers. If the valves are not changed out, the LPG can cause the brass fittings to fail, causing a fire. To compound the problem, they were not changing the placards, so a tank of LPG was transported and used with a Non-Flammable Compressed Gas placard. So be careful responding to incidents involving anhydrous farm tanks in the fall and winter. They may be carrying LPG.


In the industry, about 80% of anhydrous ammonia accidents are the result of using improper procedures, lack of training in equipment operation or failure to follow prescribed practices. Emergency responders can avoid additional injuries and death with the proper planning, training and equipment to effectively handle anhydrous ammonia emergencies.

Robert Burke, a Firehouse® contributing editor, is the fire marshal for the University of Maryland. He is a Certified Fire Protection Specialist (CFSP), Fire Inspector II, Fire Inspector III, Fire Investigator and Hazardous Materials Specialist, and has served on state and county hazardous materials response teams. Burke is a veteran of 24 years in fire and emergency services, with experience in career and volunteer departments. He has attained the rank of lieutenant, assistant chief and deputy state fire marshal. Burke is an adjunct instructor at the National Fire Academy and the Community College of Baltimore, Catonsville Campus, and the author of the textbooks Hazardous Materials Chemistry for Emergency Responders and Counter-Terrorism for Emergency Responders. He can be reached in the Internet at: robert.burke@att.net.