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Ammonia detection

An Overview of ApplicationsAmmonia is widelyused in industrialprocesses such as re-frigeration, food man-ufacturing and thechemical industry.Despite its many ad-vantages, ammonia is ahazardous chemicaland must always behandled in a safe man-ner. A need for ammo-nia monitoring also ex-ists in livestock facili-ties such as pig, poul-try and cattle farms,where ammonia is pro-duced through biologi-cal decomposition.

Liisa Åström, M. Sc. (Chem. Eng.)Application EngineerSensor Systems DivisionVaisala HelsinkiFinland

ypical symptoms ofammonia exposureare irritation of theeyes, throat and res-

piratory organs. Reliable ammo-nia detection is essential in orderto ensure both personnel andproduct safety in environmentswhere ammonia is present.

Ammonia has a low odorthreshold; concentrations aslow as 5 ppm may be detectedby the nose. At a concentrationof a few hundred ppms, irrita-tion of the mucous membraneof the eyes occurs. Breathingbecomes intolerable at approxi-mately 1000 ppm, and at thisstage vision may also be im-

Ammonia is widely used as a refrigerant in e.g. cold stores. P H O T O C O U R T E S Y O F H U U R R E G R O U P , F I N L A N D .

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and personnel safety risks causedby ammonia leaks, on-line am-monia detection should be per-formed in the cold storage.

In ice-cream factories, for ex-ample, the refrigerant is presentat the process site itself. Allequipment is washed regularlyand instruments must have ahigh tolerance against spraywater and humidity. Other aro-mas and odors are also present,placing requirements on the se-lectivity of the detector.

Good air quality for animals

Ammonia is released by anaero-bic decomposition from themanure of livestock such as cat-tle, pigs and poultry. Ammoniamonitoring is important for thewell-being of livestock. Studieseven suggest that the stresscaused by adverse surroundingsmay result in quality defects ofthe meat. High ammonia con-centrations have also beenfound to slow down the growthof e.g. poultry, which then hasdirect consequences on the pro-ductivity of the business.

Many industries use ammonia

In addition to the applicationsmentioned above, ammonia isused in many other industrialprocesses. Regarding volumes,the main user is the chemicalindustry. Ammonia is also usedin the power industry to re-move toxic nitric oxide emis-sions from stack gases by con-verting the pollutant into nitro-gen and water.

In all applications related toammonia production, storageand transport, an ammonia de-tector may be needed to ensurethat the level of ammonia in airis on an acceptable level. �

Country Standard Max. concentration in a time frame

Europe Finland HTP 25 ppm / 8 hours40 ppm/ 15 min

Germany MAK 50 ppm/ 8 hoursUK TWA 25 ppm / 8 hours

STEL 35 ppm/ 15 minSweden Nivågränsvärde 25 ppm/ 8 hours

Takgränsvärde 50 ppm/ 15 minUSA TWA 25 ppm / 8 hours

STEL 35 ppm/ 15 minPEL 50 ppm

Japan Ministry of LaborRecommendation 50 ppm

TWA = Time-Weighted AverageSTEL = Short Term Exposure LimitPEL = Permissible Exposure Limit

Table 1. Occupational safety limits for ammonia.

paired. Exposure to a concen-tration of around 2500 ppmrapidly increases the risk of fa-tality.

Occupational safety legisla-tion regulates the exposure ofpersonnel to ammonia. Safetylimits in some countries arelisted in table 1.

Ammonia is atraditional refrigerant

Ammonia has been used for re-frigeration throughout the 20th

century in a variety of applica-tions such as cold stores, icecream plants, slaughterhouses,

breweries, ice rinks etc. Am-monia has good thermody-namic properties and toleranceagainst small amounts of hu-midity and contaminants. Dueto the level of expertise re-quired in system design andoperation, it is mainly used inlarge industrial refrigerationsystems.

Ammonia is considered tobe one of the environmentally-friendly refrigerants, since itneither depletes the ozonelayer nor contributes to globalwarming. The legislative restric-tions on chlorine-containingrefrigerants (so called freons)

have focused attention on am-monia again and new installa-tions are increasingly designedto operate with ammonia.However, because it is a haz-ardous chemical, ammoniamust be monitored and thealarm given if leaks are detectedin the system. With a reliableammonia sensor, ammonia-based refrigeration systems pro-vide safe, efficient and environ-mentally-friendly cooling.

Ammonia detection in a refrigeration system

The most common installationsite for an ammonia detector isin the compressor room, wherethe core of the refrigeration sys-tem is installed. From the com-pressor room, the refrigerantsystem further connects to thecold space where heat transferoccurs in connection with thephase change of ammonia. Toavoid leaks, product spoilage

Occupational safety limits regulate the exposure of personnel to ammonia.

Ammonia iscommonly usedas a coolingagent at icerings.

P H O T O C O U R T E S Y O F VA L I O LT D , F I N L A N D .

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