Ammonia Poisoning: Symptoms and Treatment

Ammonia (NH₃) is a colorless gas with a pungent, ammonia-like odor. It is highly soluble in water to form an alkaline solution (ammonium hydroxide) and is a strong irritant/corrosive to the eyes and respiratory tract. Inhalation of high concentrations results in upper respiratory tract edema, chemical pneumonitis, and noncardiogenic pulmonary edema. There is no specific antidote; treatment is cessation of exposure, oxygen, airway protection, bronchodilators, and observation. [1]

Ammonia has a low odor threshold: most people detect it long before dangerous levels, although sensitivity may decrease with prolonged exposure. The gas is lighter than air (relative density ~0.60), so it tends to rise in rooms, but localized plumes and turbulence can create "pockets" of high concentration. [2]

In everyday life, sources include ammonia-based cleaning products and glass cleaners; in industry, these include refrigeration units using anhydrous ammonia, fertilizers, the pulp and paper industry, and water treatment. Leaks in confined spaces and spraying/heating are critical. A particular risk is mixing ammonia with bleach (hypochlorite): chloramines are formed, which are a severe irritant. [3]

Occupational exposure limits: OSHA PEL 50 ppm (8-hr TWA); NIOSH REL 25 ppm (TWA) and 35 ppm (STEL); IDLH 300-500 ppm (historically 500; the current NIOSH IDLH page describes the criteria and lower limit of hazard). For the general population, the AEGLs are: AEGL-1 = 30 ppm (10 min-8 h), AEGL-2 = 220 → 110 ppm (depending on duration), AEGL-3 = 2700 → 390 ppm. [4]

Epidemiology

Ammonia is one of the most common causes of inhalation injuries in industry (refrigeration systems, fertilizers) and in transport accidents. In the home, localized irritation episodes most often occur during cleaning or accidental spraying of concentrate in small rooms. Leaks of anhydrous ammonia are accompanied by mass exposures and hospitalizations due to respiratory tract edema. [5]

Most household cases are mild to moderate, due to the off-putting odor that stops work. However, with loss of smell or prolonged exposure, the protective effect of odor is reduced: cases of delayed deterioration with the development of pneumonitis within 6-24 hours have been reported. [6]

In the workplace, adherence to TWA/STEL and personnel training (emergency response plans, spill evacuation, closing valves and applying water to flares/sprayers) significantly reduce the number of severe outcomes. [7]

Reasons

1. Accidental releases of anhydrous ammonia in refrigeration units, warehouses/railway tanks, and fertilizer production. [8]
2. Spraying/heating ammonia solutions (detergents, glass cleaners) in small, poorly ventilated areas. [9]
3. Mixing with bleach (NaOCl) → chloramines (severe respiratory damage). [10]
4. Operating errors: lack of exhaust ventilation, lack of/incorrect PPE, work in confined spaces. [11]

Risk factors

• Confined spaces and poor ventilation (process chambers, sanitary facilities). [12]
• Aerosolization (sprays, pressurized leaks), contact with liquid ammonia (thermochemical burns of eyes/skin). [13]
• Asthma/COPD, children, elderly - more severe course. [14]
• Lack of awareness about incompatibility with hypochlorite (household bleach). [15]

Pathogenesis

Ammonia, when combined with mucous membrane moisture, forms alkaline solutions (NH₄OH), causing coagulative necrosis and inflammation. Direct causticity leads to laryngeal/tracheobronchial edema, bronchospasm, and surfactant dysfunction; at high doses, chemical pneumonitis/pulmonary edema develops. [16]

Pain, lacrimation, and burning sensation appear rapidly (seconds to minutes), but respiratory deterioration may be delayed (hours), so even with apparent improvement, observation is required. Systemic toxicity is secondary (hypoxemia, stress response). [17]

Symptoms

• Mild/moderate: lacrimation, burning in the nasopharynx, cough, hoarseness, chest pain, headache. [18]
• More severe: wheezing/shortness of breath, stridor, nausea/vomiting, dysphagia; eye pain/redness, blurred vision.
• Severe: laryngospasm, foamy sputum, hypoxemia, pulmonary edema, possible loss of consciousness. [19]
• Delayed (6-24 h): progressive dyspnea/infiltrates on imaging with initially mild symptoms.[20]

Forms and stages

1. Purely irritant (upper DP/eyes) - most common with short household contacts.
2. Lower respiratory - bronchospasm, chemical pneumonitis, non-cardiogenic pulmonary edema.
3. Mixed - gas + aerosol/liquid (eye/skin burns + inhalation).
4. Chloramines (when mixed with hypochlorite) are a clinically severe irritant, similar to chlorine. [21]

Complications and consequences

• Acute: laryngospasm/asphyxia, chemical pneumonitis, pulmonary edema; corneal/conjunctival burns. [22]
• Subacute: secondary bacterial infection, lingering cough/wheezing.
• Long-term: RADS (reactive airways dysfunction)/asthma exacerbation, rare persistent voice disturbances.

Diagnostics

The diagnosis is scenario-based: was there an ammonia odor, a spray/leak, a confined space, mixing with bleach, or eye/skin burns. There are no specific "quick" tests for NH₃ in the body—the decision is made based on the clinical examination. [23]

Minimum for symptomatic patients: pulse oximetry; blood gases in severe cases; chest X-ray/CT scan for signs of lower respiratory tract damage (or repeat after 6-12 hours if in doubt); ECG for hypoxia. Ophthalmologist for eye complaints. The hospitalization threshold is lower for children, pregnant women, asthmatics, and those exposed in a confined space. [24]

Differential diagnosis

• Chlorine/chloramines (often from mixing bleach and ammonia) - similar clinical picture; context is important. [25]
• Sulfur dioxide, nitrogen oxides - other sources and dynamics (NO₂ - typically late deterioration up to 24-48 hours).
• Asthma/viral tracheobronchitis - no apparent chemical exposure.

Treatment

1) Safety and termination of exposure.

• Evacuate to fresh air, ensure cross-ventilation; rescuers should wear personal protective equipment (PPE) if concentrations are unknown or high. Remove contaminated clothing. In case of contact with eyes or skin, rinse with plenty of water for at least 15 minutes. Do not use acid neutralization. [26]

2) Airway and oxygenation.

• 100% oxygen via a mask with a reservoir, SatO₂ monitoring. In case of hoarseness/stridor - low intubation threshold (burn of the upper respiratory tract tends to progress). [27]

3) Control of bronchospasm and pain.

• Inhaled β₂-agonists (± ipratropium) for wheezing/dyspnoea.
• Systemic glucocorticosteroids may be used selectively in cases of severe obstructive component/RADS; there is no universal evidence for routine use.
• Antibiotics are not prescribed prophylactically - only when there are clear signs of infection. [28]

4) Observation/hospitalization.

• Due to the risk of delayed pulmonary edema, observe for 6-12 hours for any significant symptoms or confinement; if worsening, re-evaluate with X-ray. [29]

5) Special remarks.

• In the bleach + ammonia scenario, the tactics are the same as for chloramines/chlorine: oxygen, respiratory protection, bronchodilators, observation. [30]

Table 1. Exposure limits and guidelines (NH₃)

Indicator	Meaning	Comment
OSHA PEL (8-hour TWA)	50 ppm (35 mg/m³)	Legal limit in the US [31]
NIOSH REL (TWA/STEL)	25/35 ppm	Recommended limits (stricter than OSHA) [32]
IDLH (NIOSH)	≈300-500 ppm	Immediately dangerous level (taking into account the explosion hazard) [33]
AEGL-1 (10 min-8 h)	30 ppm	Discomfort/irritation among the population [34]
AEGL-2 (10 min-8 h)	220 → 110 ppm	Pronounced, potentially irreversible effects (time-dependent) [35]
AEGL-3 (10 min-8 h)	2700 → 390 ppm	Life-threatening (time-dependent) [36]

Table 2. Symptoms and tactics by severity

Heaviness	Main features	Actions
Light	Tearing, burning in the throat, cough	Fresh air, eye/skin wash, observation for 2-4 hours
Moderate	Wheezing, shortness of breath, hoarseness	O₂, inhaled bronchodilators, observation for 6-12 hours
Heavy	Stridor, foamy sputum, hypoxemia	ABC, early intubation, intensive care

Prevention

Engineering measures. All work with ammonia should be carried out under local exhaust ventilation (LEV), with leak detectors, emergency ventilation plans, and personnel training. For anhydrous ammonia, containment/evacuation readiness and practiced exit routes should be in place. In the workplace, adhere to OSHA/NIOSH limits, regularly inspect RPE, and conduct spill drills. [37]

Household and cleaning. Do not spray concentrates in small rooms without a fume hood. Never mix ammonia with bleach (chloramines!), and read labels carefully. If the odor persists, ventilate or leave the room; store chemicals separately. [38]

Forecast

With mild to moderate exposures (short-term cleaning, odor spike), symptoms usually completely regress within hours to days after cessation of contact and basic support (oxygen as indicated, bronchodilators). There are generally no lasting consequences. [39]

Severe cases are associated with anhydrous ammonia leaks/aerosolization in confined spaces and with chloramines when mixed with bleach; risks include pulmonary edema and eye damage. Early oxygen, airway protection, and observation for 6-12 hours significantly improve outcomes. [40]

FAQ

• Is ammonia lighter or heavier than air - where does the gas go?

Ammonia is lighter than air (density ~0.60) and tends to rise, but leaks can form local clouds; always provide cross ventilation and evacuate the area. [41]

• What to do if ammonia gets into your eyes/on your skin?

Rinse immediately with water for at least 15 minutes, remove contaminated lenses/clothing; if pain/blurred vision occurs, consult an ophthalmologist immediately. [42]

• Can the fumes be neutralized with acid/vinegar?

No. "Home neutralization" is dangerous: heat and additional gases may be released. The only reliable course of action is to stop exposure, ventilate the area, rinse with water, and seek medical attention if symptoms develop. [43]

• What levels at work are considered dangerous?

Use NIOSH 25/35 ppm (TWA/STEL), OSHA PEL 50 ppm, IDLH ≈300-500 ppm; for the general population - AEGL-1 = 30 ppm. If there is a risk of exceeding the limit, take engineering measures and personal protective equipment. [44]