Detecting Toxic Gas with Open Path Systems


In February 2015, a Coca-Cola bottling plant in Speedway, Indianapolis initiated emergency procedures after a strong ammonia smell was sensed by 25 workers. The plant was immediately evacuated and a significant emergency response was provided by local Fire Department and Hazmat teams. The source of the leak was an 80,000 gallon tank, which was used in the refrigeration processes within the plant. Concentration readings fell from 700 ppm to about Photography courtesy of Piho Engineering 150 ppm, which was significant, though the plant could not be operated until they were further reduced to below 25 ppm. Throughout the incident, no threat was posed to anyone outside the plant, where readings were 2 ppm.

Another example of an industrial ammonia leak occurred in a frozen storage and logistics business in Shanghai, China in August, 2013 The chemical was used in food refrigeration involved in the importing, exporting, storage, and processing of seafood. A detached pipe cap caused a huge leak, as reported by the Shanghai Municipality Information Office, and led to the deaths of 15 people and injuring an additional 25.

In November 2014, a large amount of Hydrogen sulfide (H2S) blanketed most parts of Moscow, Russia where emergency authorities directed everyone to stay indoors. It was later discovered that the gas had originated in a Moscow oil refinery but no injuries occurred.

In May 2014, an oilfield worker in the municipality of Hazelwood, in the province of Alberta, Canada was found unresponsive at one of the customer worksites. It appears that the worker died from exposure to high levels of H2S.

While toxic gases may have many benefits and useful applications within a variety of industries, high concentrations can cause significant damage to humans and be life threatening.

Two particular examples of toxic gases commonly present in industrial and agricultural environments are ammonia and hydrogen sulfide. Ammonia is utilized in various industries in a wide range of processes, either as raw product or a byproduct. These include carbon capture and storage in the oil and gas industry, fertilizer, nitric acid, explosive, plastic production and more. Ammonia, NH3, in gaseous form is a colorless gas with a characteristic smell.

However, operating staff often debate about which type of device to select and where to place the sensors for best coverage. The confusion stems in part from the wide range of flammable materials that process plants may handle; a single process area may contain several different types. In addition, the development of new technologies like visual flame imaging and pattern recognition, while improving identification effectiveness, has created uncertainty around the choice of flame detectors. Fortunately, the particular application rather than detection technology determines the proper pick. In this article, we’ll examine the criteria for selection and review the detector types commonly used to protect against industrial fires.

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