Dangers of Ammonia
The dangers of ammonia are caused by its flammability, toxicity and potential to be at extremely low temperatures. This section will cover each of those.
Flammability
While ammonia is not normally considered a flammable gas it does have a flammability limit between 15% and 28%. That is to say, if the concentration of ammonia is between those two amounts a spark would ignite it in an explosive fashion. This is an extremely narrow band compared to hydrocarbons, and as such the flammability is not usually considered a primary concern in the event of an ammonia release.
The addition of lubricating oils found in ammonia refrigeration systems in an aersolised fashion (broken apart into small droplets by pressure) can significantly increase the ranges of the flammability limit and making the situation more likely to occur. Laboratory testing has shown that the lubricating oils from compressors when suspended as a fine mist can lower the limit to 10% and raise the upper limit.
The highest risks for an ammonia explosion are:
Confined machinery rooms with inadequate ventilation where a small continuous leak is allowed to accumulate.
Catastrophic line rupture producing a drifting gas cloud that passes an ignition source while still within the 15–28 % envelope.
Hot-work on charged equipment—welding, grinding, or cutting on vessels or piping that has not been properly isolated and purged.
While an ammonia explosion is an extremely deadly situation it is unlikely however that a worker without SCBA (self contained breathing apparatus) would find themselves immersed in an atmosphere of ammonia in those concentrations as the Immediately Dangerous to Life and Health limit for ammonia is 0.03% (300ppm). To put it bluntly, you would likely be killed by the gases toxic properties at a concentration well before you have the chance to be killed by an explosion.
Toxicity
The toxicity issues with ammonia can be broadly divided into respiratory exposure and skin/eye contact. Respiratory exposure is the form most likely to seriously kill or injure someone and safety processes focus more on preventing inhalation than treating it afterwards. Skin and eye contact are usually less immediately dangerous and initial treatment is far simpler to apply in an industry setting.
Respiratory
Ammonia’s first warning sign is its sharp, pungent odour, detectable by most people at 0.5 – 5 ppm (0.00005 – 0.0005 %). Eye and throat irritation build with concentration and exposure time:
5 ppm (0.0005%)
Odour threshold; mild throat “tickle” after several minutes
25 ppm (0.0025%)
Eyes water; irritation felt almost immediately. This is the maximum limit for a worker on a standard 8 hour shift
35 ppm (0.0035%)
Marked discomfort within minutes. This is the 15 minute short-term exposure limit (15-min STEL)
50 - 100 ppm (0.005–0.01%)
Coughing, chest tightness, shortness of breath.
300 ppm (0.03%)
Lung fluid build-up (pulmonary oedema) starts; collapse possible in < 30 min
700 ppm (0.07%)
Rapid respiratory distress; fatal exposure in < 30 min
Over 2500 ppm (≥0.25%)
Death in seconds to a few minutes
Above 100 ppm many people experience what is called "olfactory fatigue" which essentially means your nose just switches off, giving the false sense that the leak has cleared. For this reason you should never rely solely on smell to determine if an ammonia leak has been dealt with and instead calibrated detectors should be used.
Skin and Eye Contact
Liquid ammonia or condensate on moist skin forms high-pH ammonium hydroxide (pH ≈ 11–12), producing both chemical and cold-burn injury. Pain can be deceptive: tissue damage often extends beneath intact skin and may not declare its full severity for 24–48 h.
For the eyes, even a 1-second splash at ~10 % volume ammonia can raise corneal pH above 11 and start protein denaturation (protein denaturation is where the proteins lose their structure and coagulate, for example cooking an egg white.) Delayed irrigation, even by as little as 30 seconds, dramatically worsens prognosis, progressing from temporary redness to corneal opacity or perforation. Lets have a look at some possible exposure scenarios.
Vapour ≤ 500 ppm contacting sweaty skin
The immediate effects will be stinging and whitening causing a "frosted" appearance. The likely outcome is a superficial alkali burn which heals in days if flushed promptly.
Splash of anhydrous liquid (–33 °C)
Instant freezing, waxy skin and numbness, potentially causing deep tissue necrosis, possibly requiring amputation
Eye splash with liquid or > 10 % vapour
Causes severe pain, blepharospasm (involuntary closure of the eyelids) or blurred vision, possibly resulting in permanent corneal scarring or blindness
The best way to avoid dangerous and damaging outcomes from direct contact with ammonia is to prevent the contact occurring in the first place.
PPE
For most sites handling ammonia the expected exposure for workers is below 25ppm in routine conditions. At this level it is considered unnecessary to wear respiratory protection so things such as air-purifying respirators are normally not worn. If cartridge style respirators are being used during normal operation (usually for short term operations above 25ppm) the cartridge must be replaced as soon as odour can be detected inside the mask.
However, in the event of an ammonia leak (during which ammonia levels may be significantly higher than is acceptable for normal exposure limits) SCBA is required to protect the persons entering the environment. If ammonia levels are unknown, for example due to a burst line, entering a confined space or attempting an emergency rescue then SCBA should be worn at all times. Under no circumstances should you attempt to operate without SCBA in an environment over 300ppm.
Even during planned maintenance where hot work or line-breaking is planned on potentially charged equipment SCBA should be worn, as this can result in sudden local increases in the concentration of ammonia, a situation that has caused fatalities in the past.
SCBA intended for use in an ammonia environment should have two sets available in order to allow use of a "buddy" system. Operators should only enter these environments in pairs to ensure that in the event of something going wrong there is the opportunity to rescue the person who has been injured.
First Aid
The steps for first aid in the event of ammonia exposure vary depending on the type of exposure the victim has suffered.
Inhalation
Fresh air immediately – Move the casualty upwind; keep them warm and at rest.
Loosen clothing – Ease tight collars, belts; monitor breathing.
Oxygen – If trained and cylinders are available, give high-flow O₂.
CPR ready – If breathing stops, begin CPR.
Transport – Ambulance to hospital even if symptoms ease.
Note: Pulmonary oedema can develop 6–24 h post-exposure; all significant inhalations require observation.
Eye Contact
Flush Immediately – Hold eyelids open; irrigate with water for at least 15 min (≥ 30 min if liquid ammonia).
Remove lenses – If contact lenses remain after the first minute of flushing, remove them and continue rinsing.
Cover & transport – Lightly cover with sterile pad; urgent ophthalmology (eye doctor) review.
Note: Do not use neutralising solutions or ointments on site; they delay irrigation. The most effective method to remove ammonia is with water flushing due to its high solubility in water.
Skin & Frostbite
Drench & strip – Safety shower for at least 15 min while removing clothing; cut off garments stuck to frozen skin.
Re-warm frostbite – Immerse in 40 °C water only after complete decontamination and if no refreezing risk.
Dress – Sterile, loose, non-adherent dressing; avoid ointments.
Hospital – Burns specialist for deep, blistered, or areas larger than a palm.
Ingestion
Do NOT induce vomiting.
Rinse mouth thoroughly; small sips of water if conscious.
Immediate hospital; endoscopy within 12 h to assess caustic injury.