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STEL: 35ppm (Short Term exposure Limit - 15mins)

TWA: 25ppm (Time Weighted Average - 8 hrs)


Alarm Recommendations
Rising Latching Alarms for Life Safety Applications

First Alarm: Second Alarm: Third Alarm:
25ppm 35ppm optional

Ammonia NH3 MoleculeAmmonia gas is lighter than air and will rise however in the presence of moisture (such as high relative humidity). The liquefied anhydrous ammonia gas forms vapours that are heavier than air. This can increase the risk of exposure from leaks to personnel, particularly in large NH3 refrigeration plant.

Ammonia is composed of Nitrogen and Hydrogen. It is a colourless gas with a characteristic pungent smell. Ammonia (NH3) is one of the most commonly produced industrial chemicals. NH3 is very toxic and also flammable with an LEL of 16%

In the environment, Ammonia is part of the nitrogen cycle and is produced in soil from bacterial processes. NH3 is also produced naturally from decomposition of organic matter, including plants, animals and animal wastes.


Physical properties of ammonia include:

  • At room temperature, ammonia is a colourless, highly irritating gas with a pungent odour.
  • In pure form, it is known as anhydrous ammonia and readily absorbs moisture.
  • Corrosive.
  • NH3 gas is easily compressed and forms a clear liquid under pressure.
  • The gas is usually shipped as a compressed liquid in steel containers.
  • Containers of ammonia may explode when exposed to high heat.


As fewer and fewer CFCs and HCFCs are available for use as refrigerants, ammonia has become popular as a replacement. Ammonia is a cost-effective, efficient alternative to CFCs and HCFCs that is also safe for the environment.

Frequently used commercially in large freezing and refrigeration plants is also called “anhydrous ammonia” because it contains almost no water (it is 99.98% pure). Tocsin 102 Series ATEX gas detectors and 2 Wire 750 series samplers; are commonly deployed into Ammonia refrigeration plant rooms. TOC-30 safe area gas detectors and 2-Wire 750 sampler series are commonly deployed to monitor Ammonia valve stations and evaporators.

As a refrigerant, Ammonia has many advantages over CFCs and HCFCs:

  • An ammonia-based refrigeration systems costs 10-20% less to build than one that uses CFCs because narrower-diameter piping can be used.
  • NH3 is a 3-10% more efficient refrigerant than CFCs, so an ammonia-based system requires
  • NH3 is safe for the environment, with an Ozone Depletion Potential (ODP) rating of 0 and a Global Warming Potential (GWP) rating of 0.
  • Ammonia gas is substantially less expensive than CFCs or HCFCs


  • It is incompatible with copper, so it cannot be used in any system with copper pipes.
  • NH3 is toxic and Flammable
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