Ohio State University Extension Fact Sheet

Ohio State University Fact Sheet

Food, Agricultural and Biological Engineering

590 Woody Hayes Dr., Columbus, Ohio 43210

Safe Handling of Anhydrous Ammonia


Timothy J. Lawrence
Dr. Thomas G. Carpenter
Dr. Thomas L. Bean

Farmers throughout Ohio use anhydrous ammonia (NH3) as one source of nitrogen fertilizer for crops. All associated personnel should be familiar with the safe use of anhydrous ammonia, understand the potential for injury and know how to respond to an emergency. Anhydrous ammonia is caustic and will cause severe bums to the eyes, skin and respiratory tract. Anhydrous ammonia is a strong alkali that can cause death or severe injury to body tissue due to its caustic, corrosive, freezing and dehydrating action. Its strong affinity for water and rapid evaporation creates an almost instant freeze-drying process when the liquid NH3 comes in contact with body tissue.

Stored as a liquid under pressure, NH3 vaporizes to a colorless gas at atmospheric pressure and a temperature of -28 degrees F. It is important to understand that vapor pressure of NH3 will increase as the temperature increases. The pressure relief valve on the tanks are set to open at 250 psig. This pressure will be reached if the tank temperature reaches 116 degrees F (see graph below). Conditions that permit tank temperatures to increase drastically (i.e., left in the direct sunlight during very hot days) should be avoided.

As temperature increases, the vapor pressure of the anhydrous
ammonia in the nurse tank increases. At 116 degrees F the pressure in
the tank will reach 250 psig and anhydrous ammonia will be released.

Ammonia dissolved in water will react readily with copper, zinc, brass and many alloys. Only non-galvanized steel or iron should be used for containers, fittings and piping (Schedule 80 pipe or Schedule 40 when welded by a certified welder). All materials used with anhydrous ammonia should conform to recommended standards. Anhydrous ammonia tanks should not be used to store other materials such as propane or liquefied petroleum gas.

Accident Situations

The accidental release of anhydrous ammonia can create a dangerous situation for both the handler and bystanders. The following situations are dangerous:

An estimated eighty percent of reported accidents result from improper procedure, lack of knowledge or training, and failure to follow proper safety precautions. Accidents can be reduced if all individuals follow safety rules and maintain the equipment properly. It is essential that all equipment be in good operating condition. Only trained individuals should handle and apply anhydrous ammonia.

Personal Protection

Goggles, rubber gloves, and complete protective clothing are necessary when handling anhydrous ammonia. It is recommended that goggles and a face shield or an approved respirator be used to protect the eyes and face from a direct blast of ammonia that can permanently blind and disfigure an individual.

Water must be available for flushing the eyes and skin in case of exposure. Each vehicle used for anhydrous ammonia must carry a five-gallon container of clean water. Anyone handling NH3 should carry a six to eight-ounce squeeze bottle of water in their shirt pocket for rapid emergency access.

Washing with water is the emergency measure to use when skin or eyes are exposed to anhydrous ammonia. Time is important! Get water onto the exposed area of the skin or eyes immediately and flush for at least 15 minutes. Never wear contact lenses when handling anhydrous ammonia, since they can trap the gas and freeze the contacts to the eye. Contaminated clothing should be removed quickly but carefully. Thaw clothing frozen to the skin with water before attempting removal. Wash the affected skin area with abundant amounts of water and do not apply anything except water for the first 24 hours. Stay warm and get to a physician immediately.

Care and Maintenance of NH3 Tank

Anhydrous ammonia can be handled and used safely. It is imperative that all equipment is properly maintained and checked daily. A regular, scheduled maintenance program will ensure that all the valves and the tank are safe for handling the high pressure liquid and its vapor form. Perform a daily visual inspection to locate any defects in the tank or hoses. To handle NH3 safely, all equipment must function properly. The most important valves and components that must be routinely checked are listed below. For a more detailed explanation, refer to External Visual Inspection Guidelines for Anhydrous Ammonia Nurse Tanks Applicators Tank Appurtenances, published by:

The Fertilizer Institute (TFI)
501 2nd St. N.E.
Washington, D.C. 20002

Important Valves And Components List


Labels, Marking & Safety Signs Legal Requirements

Nurse tanks must be labeled "ANHYDROUS AMMONIA" in 4 inch letters, on contrasting background , on the sides and rear of the tank. Federal DOT regulations require the words "INHALATION HAZARD", in association with the anhydrous ammonia label, in three inch lettering be placed on both sides of the tank. A Non-Flammable Gas placard with the numbers 1005 (identifying it as anhydrous ammonia) must be located on both sides and both ends of the tank. A Slow Moving Vehicle (SMV) sign must be prominently displayed on the rear of the tank with the bottom of the sign at least 2 and not more than 6 feet from the ground.. The valves must be appropriately labeled by color or legend as vapor (Safety Yellow) or liquid (Omaha Orange). The letters of the legend must be at least 2 inches high on contrasting background and within 12 inches of the valves.

Standard Recommendations

The American Society of Agricultural Engineers (ASAE) has developed a number of general safety standards which contain requirements that should be applied to anhydrous equipment. ASAE S441 establishes requirements for uniform safety signs to promote safety of persons associated with agricultural equipments. This includes:

These safety signs should be strategically placed in the immediate vicinity of the hazard and be readily visible so that the viewer can avoid the hazard or take other appropriate action. In consideration of these requirements and the multiple concerns for various safe operating procedures mentioned previously, several standard safety signs (illustrated below) should appear on the equipment used in handling and application of anhydrous ammonia.

Additional ASAE safety standards require the following:

Highway Safety

The speed limit for anhydrous ammonia tanks traveling on the public roadways of Ohio is 25 M.P.H. and only one nurse tank may be towed. Prior to operating a nurse tank on public roadways the following should be carefully checked:

Running Gear - Inspect the farm wagon frame tongue, reach poles, anchor devices, wheel bearings, knuckles, ball joints and pins for structural damage, cracks, excessive wear and adjustments.

Tires - Check for proper inflation, cuts, badly worn spots, and signs of weathering. Assure that lug nuts are tight.

Lubrication - Steering knuckles, wheels, tongues, or other applicable farm wagon equipment should be lubricated at least once every year.

It is highly recommended that the vehicle used to tow the nurse tank be at least equal in weight to the gross weight of the nurse tank. This will assist the operator in maintaining control of all the vehicles, at 25 M.P.H., and minimize the potential for an accident.

Any tank operating on the highways should look similar to the above drawing. Regulations require: An SMV emblem be attached to the rear of the vehicle and visible from at least 500 feet; The words Anhydrous Ammonia (4 inches high) in contrasting colors be placed on both sides and the rear of the tank; The words Inhalation Hazard (3 inches high) in association with the anhydrous ammonia label be on both sides of the tank; The DOT placard for non-flammable gas be placed on the front, back and sides of the tank.

All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.

Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.

TDD No. 800-589-8292 (Ohio only) or 614-292-6181

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