What should be done in case of an ammonia leak?

For ease of transportation and storage, gaseous ammonia is commonly liquefied by pressurization or cooling to produce liquid ammonia. During vaporization, liquid ammonia absorbs substantial heat; thus, ammonia can serve as a refrigerant. When the (volume) concentration of ammonia in air reaches 0.6%, exposure for half an hour causes poisoning; at 11–14%, it becomes flammable; and at 16–25%, it may explode upon contact with an ignition source. Moreover, at high temperatures (260°C), ammonia decomposes to release hydrogen gas (H₂), which—when mixed with air and exposed to an ignition source—can cause violent explosions. Virtually all industrial ammonia production employs the Haber process: synthesis from nitrogen and hydrogen gases under high pressure, elevated temperature, and in the presence of a catalyst. Nitrogen is primarily sourced from air; hydrogen mainly comes from syngas containing hydrogen and carbon monoxide (pure hydrogen may also be obtained via water electrolysis). The mixture of nitrogen and hydrogen gases constitutes the synthesis gas (feedstock) for ammonia production. Raw gas derived from fuel and chemical industries contains sulfur compounds and carbon oxides, which are catalyst poisons for ammonia synthesis; therefore, thorough purification is required prior to ammonia synthesis.

What hazards does ammonia leakage pose, and how can it be prevented?

Characteristics of Ammonia: Ammonia ranks among the hazardous chemicals most frequently involved in industrial accidents in China. Also known as liquid ammonia, it is a toxic and flammable gas with broad applications: it serves as a raw material for ammonium salts, ammonium nitrate, urea, and as a refrigerant in cold-storage facilities. It is colorless, possesses a pungent, irritating odor, exhibits strong alkalinity in its liquid state, forms explosive mixtures with air, and can ignite or explode upon exposure to open flame or high temperature. Ammonia is highly corrosive and irritates or corrodes any skin tissue it contacts. Following ammonia poisoning, individuals experience pronounced irritation in the throat and mouth. Inhaled ammonia readily crosses the alveolar membrane into the bloodstream, binds to hemoglobin, and impairs oxygen transport. Short-term inhalation of high-concentration ammonia may cause tearing, sore throat, hoarseness, coughing, blood-tinged sputum, chest tightness, and breathing difficulty; severe cases may progress to pulmonary edema. An airborne ammonia concentration of 500–700 mg/m³ may result in ‘lightning-fast’ death; excessive ammonia inhalation elevates blood ammonia levels, potentially triggering cardiac arrest and respiratory failure—endangering life. Hazards and Prevention Measures for Ammonia Leakage Accidents: Hazards of Ammonia Leakage: (1) Rapid Vaporization and Dispersion Upon leakage, ammonia transitions rapidly from liquid to gas phase. Liquid ammonia vaporizes swiftly, expanding dramatically in volume; unvaporized liquid ammonia forms fine droplets dispersed within the vapor cloud. During initial leakage, partial evaporation renders the ammonia vapor cloud denser than air, causing it to drift downwind and easily form extensive contamination zones and fire/explosion hazard areas. On July 8, 2002, at a Shandong fertilizer plant, a 20-cubic-meter liquid ammonia storage tank was being filled into a tanker truck when the truck’s metal flexible hose ruptured. Liquid ammonia rapidly dispersed, enveloping the entire plant site within minutes and threatening the lives of 2,000 people. This incident caused 105 poisonings, 13 fatalities, 24 severe injuries, and 12 moderate injuries. (2) High Toxicity and Risk of Casualties Ammonia is a toxic, irritating, foul-smelling, and highly volatile gas. Once leaked into the atmosphere, it spreads over wide areas, posing risks of acute poisoning and chemical burns. The maximum permissible concentration in air is 30 mg/m³. Inhalation of air containing 0.5–0.6% ammonia for 30 minutes suffices to cause poisoning. Primary routes of human exposure include skin contact, sensory organs, respiratory tract, and digestive tract. Mild poisoning symptoms include dry, burning sensations in eyes and mouth, lacrimation, rhinorrhea, coughing, hoarseness, dysphagia, dizziness, and headache; clinical examination reveals conjunctival hyperemia and edema, and occasionally dry rales on auscultation of the lungs. Severe poisoning—induced by high-concentration exposure—may cause second-degree chemical burns on exposed areas such as the head and face, accompanied by coma, mental confusion, convulsions, myocarditis, or heart failure; a few cases result in instantaneous death due to reflex laryngospasm or respiratory arrest. (3) Flammability and Explosivity Ammonia is both toxic and flammable. Its autoignition temperature is 651°C; its calorific value is 2.37–2.51 J/m³; its critical temperature is 132.5°C; and its critical pressure is 11.4 MPa. When ammonia constitutes 11–14% of air volume, it ignites readily upon contact with an ignition source, producing a yellow-green flame; the presence of oils significantly increases fire risk. At concentrations of 15.7–27.4% in air, ammonia will explode upon encountering an ignition source; the minimum ignition concentration is 17%, generating a peak explosion pressure of 0.58 MPa. Heating liquid ammonia containers causes internal pressure to rise, potentially resulting in catastrophic rupture or explosion of steel cylinders or storage tanks.

Fire at Oregon Seafood Plant Forces Evacuations Amid Ammonia Exposure Fears

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A fire at Pacific Seafood's Oregon facility triggered evacuations due to fears of ruptured ammonia tanks. All employees were safe, though the company expects major losses as firefighters contained the blaze.

apnews

2026-10-26

Fire at Oregon Seafood Plant Forces Evacuations Amid Ammonia Exposure Fears

Fire at Oregon Seafood Plant Forces Evacuations Amid Ammonia Exposure Fears

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