Gas Detection Technology

The choice of gas detection technology is also a complex decision and can be influenced by the choice of single point or multi-point sampling since that choice can lock you into a certain group of commercially available gas detectors or monitoring systems. 

Director or Indirect Gas Detection. In selecting a gas detector, it is important to note whether a detector responds to the target gas directly or indirectly. For example, in monitoring for phosphorous pentafluoride, an indirect gas detector might detect hydrogen fluoride (a by-product created when phosphorous pentafluoride comes in contact with moisture in the air). In order for this indirect gas detector to provide satisfactory protection, the proper environmental conditions, such as a sufficient humidity level, must exist in the monitored area.t Sometimes gas detectors are selected to monitor for the presence of a carrier gas used in conjunction with the actual target gas. Care must be taken withthis approach since carrier gas detection characteristics and limits relative to the target gas may not afford adequate protection. 

Identify All Interferents. The type and affect of interferinggases or vapors can also influence the choice of gas detection technology. A gas detector, with an interferent response characteristic similar to Fig. 13, would probably be a poor choice in an area where equipment and other surfaces are wiped down with an isopropyl alcohol solution, and could be the source of frequent false alarms. 

Sensitivity and Resolution. The detection sensitivity and resolution of a gas detector must match the monitoring requirements for the target gas and provide an acceptable margin of safety in the event of atoxic gas leak. If a gas with a TLV of 50 parts per billion (PPB) requires monitoring and the established alarm setpoint is one half the TLV (i.e., 25 PPB), a gas detector with sensitivity and resolution in parts per million would be totally inadequate for the application. 

Factors such as stability, detection speed, recovery time, frequency and methods of calibration, required maintenance, and reliability can also influence the selection of a specific gasdetection technology. 

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When the decision is made to install an automatic detection system, the fire/gas detection technology should be carefully selected to match the expected hazard and the environment in which it will be installed. The design and installation of a reliable fire/gas detection system in an industrial facility should only be done by experienced personnel. Otherwise, the facility owner may have an inappropriate system and may be plagued by nuisance alarms and high maintenance costs. 

Hydrogen gas detectors located in your work area can provide warnings of any system leaks. In-line gas detectors, either hydrogen or oxygen, can provide information on the purity of the gases in the system. The most common gas detection technologies are electrochemical and catalytic. 

Gas monitoring systems should be chosen to suit their intended use since significant differences exist between available sensing technologies, price, and performance. There are basically two types of gas detection technologies. With instrumentation monitors, a sample of air is drawn through a piece of tubing, the sample draw line, to an analysis instrument, which is most commonly based on mass spectrometry, flame emission spectrometry, infrared spectrometry, or colorimetric (paper tape) response. 

A portable gas detector is a critical piece of equipment meant to save your life. Despite advancements in gas detection technology, industrial workers continue to lose their lives from exposure to toxic or explosive gases. 

Gas Detection Principles. Some of the more common gas detection principles used in toxie gas monitoring include electroehemistry, electro-optical detection, solid state detection, mass spectrometry, moleeular (or flame) emission speetrometry,irrfrared speetrophotometry, ionization teeh-niques, and thermal conduetivity. Brief deseriptions of several different gas detection technologies are deseribed below. 

Detection Speed. Detection speeds can differ between various gas detection technologies and may significantly contribute to the overall response time of atoxic gas monitoring system. The selection of a specific gas detection technology can have a major impact if instantaneous response times are required. 

Recovery Time. Certain gas detection technologies require time to recover or clear after exposure to a target gas or interferent. Detection accuracy can be severely affected if a second gas leak occurs in the gas detector s monitoring area before it has recovered from the first gas leak. Thus, recovery time may influence the selection of a specific gas detection technology.b ]... 

Thus, the choice of gas detection technology, or combination of technologies, is dependent on many variables and factors. 

New gas detection technologies add flexibility and advanced options Learn methods for monitoring potentiaiiy toxic contaminants. 

Accurate air monitoring equipment and good documentation are necessary to effectively detect hazardous levels and ensure safety. To this end, new gas detection technologies have entered the market, offering more flexibility and advanced options. Several formats are available, including badges, tubes, single-and multi-gas detectors, photo-ionization detectors and combination types. 

Membrane Technology in Trace Gas Detection. Parts I I1. Evaluation of the Universal Monitor Olfax Instrument , Rept 2083, US Army Mobility Equipment R D Center, Fort Belvoir, Va (Dec 1973) AmericanLaboratory 36 (1975) 62) R.M. Burger, Ed, Comparative... 

Chambers P., Austin E.A.D., Dakin J.P., Theoretical analysis of a methane gas detection system using the complementary source modulation of correlation spectroscopy, Measurement Science and Technology 2004 15 (8) 1629-1636. 

When evaluating a facility, a review of the existing fire/gas detection system is recommended. Due to recent technology developments, the performance of fire/gas detection systems has significantly improved over the last few years. 

Electrochemical gas detection instruments have been developed which use a hydrated solid polymer electrolyte sensor cell to measure the concentration of specific gases, such as CO, in ambient air. These instruments are a spin-off of GE aerospace fuel cell technology. Since no liquid electrolyte is used, time-related problems associated with liquid electrolytes such as corrosion or containment are avoided. This paper describes the technical characteristics of the hydrated SPE cell as well as recent developments made to further improve the performance and extend the scope of applications. These recent advances include development of NO and NO2 sensor cells, and cells in which the air sample is transported by diffusion rather than a pump mechanism. 

S. Jensen, J.L. Olsen, H. Hansen, U.J. Quaade, Reaction rate enhancement of catalytic CO oxidation under forced thermal oscillations in microreactors with real time gas detection, in AIChE (Ed.), International Conference on Microreaction Technology (IMRET 8), Atlanta, 2005, p. 134h. 

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