<img src="https://secure.leadforensics.com/77233.png" alt="" style="display:none;">

NH3 Gas and its Sensor

Intro to Ammonia

Ammonia gas is a chemical compound comprised of one nitrogen and three hydrogen atoms with the formula NH3. In its pure form, ammonia is a colorless gas, but is easily identifiable by smell, as it has a pungent odor. Ammonia is normally found as a gas, which is caustic and harmful with long-term exposures, requiring a hazardous safety permit. 

Ammonia gas is commonly found in the production of fertilizers, refrigerants and cleaning solutions, however, you are likely to smell it well before it will be harmful to you. The degree of danger that ammonia gas poses varies significantly depending on how much is present, and how long you've been exposed for. 

Industrial ammonia production is one of the highest for inorganic chemicals with numerous large-scale ammonia plants worldwide producing 235 million tonnes in 2021. This is largely done through the Haber Process, an artificial nitrogen fixation process that uses hydrogen as a catalyst.  

Gas Characteristics

  • Colorless
  • Gas state
  • Compressed
  • Toxic
  • Flammable
  • Corrosive
  • Lighter than air
  • Water soluble
  • Explosive (at high concentrations and confined spaces)
  • Pungent, suffocating odor
  • Can decompose at high temperatures forming very flammable hydrogen gas
  • Ammonia based fertilizers and agricultural land management can cause emissions of nitrous oxide.
  • Ammonia molecules have a trigonal pyramid shape
  • OTHER NAMES: Anhydrous ammonia, ammonia, azane, hydrogen nitride
  • CAS 7664-41-7
icon ghs flammable - examples include nitrogen oxides, concentrated ammonia solutions, anhydrous ammonia
icon ghs toxic - examples include nitric acid which can dissolve alkali metals and cause harm to the respiratory tract of workers along with ammonium chloride
GHS corrosive WHMIS - examples include sulphuric and nitric acids including ammonium hydroxide is a corrosive gas

Industrial NH3 detection, hazards and sources

  • Farms: Ammonia produced by compost piles on mushroom farms can generate ammonia gas. Manure pits and any indoor or confined spaces where farm animals are kept can also contain ammonia gas.
  • Water treatment: Ammonia is used to produce monochloramine which is used as a disinfectant.
  • Refrigeration Systems: Ice rinks, breweries / beverage manufacturing and ice manufacturing plants use liquid ammonia / aqueous ammonia - NH3(aq). If it leaks, it becomes ammonia gas.
  • Fertilizers and Cleaners: Liquid ammonia is often diluted and combined with other chemicals.
  • Some manufacturing processes also use ammonia, including combining it with HCl or hydrochloric acid to produce ammonium chloride.
  • May be exposed to ammonia while using cleaning products that contain ammonia.
  • Other sources of occupational exposure include the silvering of mirrors, gluemaking, tanning of leather, and around nitriding furnaces.
  • Ammonia is produced as a by-product in coal distillation and by the action of steam on calcium cyanamide, and from the decomposition of nitrogenous materials.
  • Ammonia is produced naturally in soybean, evening-primrose seeds, lambsquarter, and tobacco leaves.

Ammonia leaks are on the rise due to increased use of natural refrigerants over fluorinated gas counterparts.

(Process Equipment & Control News)

High Risk Scenarios

  • Warmer buildings can produce ammonia in higher concentrations than cold buildings.
  • In an enclosed space, ammonia can explode if an ignition source is introduced.
  • Outside of an accidental release of ammonia, the potential for exposure to high concentrations of ammonia is greatest during confined space entry.
  • Technically speaking, the moment a worker breaks the plane of an opening, he or she has in fact entered a confined space, and when ammonia is involved, workers should assume that confined spaces present a hazardous environment.
  • In the event of a leak or CSE procedure, it would be a mistake to assume that ammonia’s distinct odor would serve as an adequate warning signal.
  • Gas detectors can measure the concentrations of ammonia and can quickly alert workers of changes in air quality.

NH3 Sensor Info

Type: Electrochemical
Range: 0-100 ppm (0.1 ppm resolution)
High Range: 0-500 ppm (1 ppm resolution)

Default Alarm Levels

Low Alarm: 25 ppm
High Alarm: 50 ppm
STEL — 15 minute — Short Term Exposure Limit: 35 ppm 
TWA  — 8 hour time weighted average: 25 ppm 

Blackline devices that can detect NH3

Questions about the detection of NH3?


Special Applications and Considerations

  • Slow-moving water: Slow-moving or stagnant water may have high ammonia gas concentrations because of lack of turbulence and volatilization and greater accumulation of metabolic waste and decomposition products—including ammonia (WHO 1986).
  • High density of fish: Reduced stream flow may concentrate fish into pools or other refugia, concentrating waste excretion and elevating ammonia concentrations.
  • Presence in organic wastes: Organic wastes are the remains of any once-living organism or their excrement. Ammonia excretion from the body also occurs through urine so the average concentration in domestic sewage influent is 40 mg/L. Identifying the organic matter in waterbodies or aqueous solutions aids in identifying the source.
      – Ammonia levels in water <1 mg/L can be harmful.
  • Plant material is typically low in nitrogen, and associated decomposers may take up ammonia and reduce its aqueous concentration. Identifying the type of organic waste present in a waterbody will aid in identifying candidate causes. Excessive organic wastes in water may result in a grayish cast with visible sludge deposits in depositional areas.
  • Foul odor: Ammonia gas has a characteristically pungent odor (think of window and floor cleaners). Ammonia concentrations in streams are rarely high enough to exhibit this odor, but water that has a foul, septic or organic-waste smell may have relatively high concentrations of ammonia.
  • Suspended solids: Suspended solids from wastewater effluents or runoff can contain high ammonia or act as catalysts for bacterial growth promoting accumulation of ammonia. Identifying the type of suspended material present is important in identifying candidate causes.
  • Alkaline, anoxic, or warm water: Water characteristics that promote ammonia formation (e.g., anoxia) or increase toxicity (e.g., high pH and temperature) are signs that ammonia may be a cause.
  • Ammonia solution also known as aqueous ammonia is ammonia diluted in water. It serves various purposes from being an ingredient in household cleaners, disinfectant for water treatment, food production to bring down the acidity in food, and even furniture darkening.
  • Medical uses are being tested, for example, ammonia gas is being used as a respiratory stimulant to prevent fainting.

Health Risks and Handling of NH3

0 - 0.5 ppm
Typical background levels of low concentrations.
0.6 - 23 ppm
Still considered a low concentration but can usually be detected by smell.
24 - 29 ppm
Nose and throat irritation can occasionally be detected (2-6 hours of exposure)
30 - 49 ppm
Slightly irritating to some people after 10 minutes of exposure
50 - 71 ppm
Moderately irritating to the majority of people after 10 minutes of exposure
72 - 139 ppm
Continuous exposure to NH3 can cause irritation of the nose and throat after only 5 minutes.
140 - 499 ppm
Will be unbearably irritating to most people after 30 minutes
500 - 1499 ppm
Nose and throat will immediately experience severe irritation, lacrimation occurs (crying)
1500 - 2499 ppm
Brief exposure can lead to a pulmonary edema (accumulation of fluid in the lungs, potentially fatal)
2500 - 4500 ppm
Death likely after 30+ minutes of exposure
5000ppm +
Will often cause rapid respiratory arrest, death very likely
NH3 first aid
  • Inhalation: Take precautions to ensure your own safety before attempting rescue (e.g., wear appropriate protective equipment). Move victim to fresh air. If breathing is difficult, trained personnel should administer emergency oxygen. DO NOT allow victim to move about unnecessarily. Symptoms of pulmonary edema may be delayed. Immediately call a Poison Centre or doctor. Treatment is urgently required. Transport to a hospital.
  • Skin Contact from Gas: flush with lukewarm, gently flowing water for 5 minutes. If irritation or pain persists, see a doctor. 
  • Eye Contact from Gas: immediately flush the contaminated eye(s) with lukewarm, gently flowing water for 5 minutes, while holding the eyelid(s) open. If irritation or pain persists, see a doctor. 
NH3 dangers
  • Handling: Immediately report leaks, spills, or failures of the safety equipment (e.g., ventilation system). In event of a spill or leak, immediately put on escape-type respirator and exit the area. Do NOT work alone with this product. Get medical attention for all exposures. Symptoms can be delayed. Prevent accidental contact with incompatible chemicals.


Ammonia Gas — What You Need to Know About it

Read the article

Discover The Most Advanced & Accurate Combustible Gas Detection Technology

Watch the webinar


Download the whitepaper

VOC Gases - Protect Workers Against Hidden Hazards




H2S Gas — What You Need to Know About Hydrogen Sulfide

Read the article

Hydrogen Sulfide (H2S) Exposure in the Oil and Gas Industry: Risks and Prevention

Read the article

Choosing the Right Combustible Gas Detector for Your Worksite

Read the article