Acetylene (C2H2) is used for gas welding, because the flame is easily adjustable. At the same time, acetylene is highly explosive when it mixes with oxygen or when there is a sudden change in pressure or temperature. Even at relatively low temperatures, like 306°, a little electric spark is sufficient to cause an explosion. For workers' safety the acetylene concentration has to be continuously monitored.
Early warning systems for volcanic eruptions continuously monitor CO2 by TDLS, as it is an abundant volcanic gas.[ 115 ]
SO2 is a highly reactive and toxic gas which leads to severe respiratory disorders, hence its emissions have to be controlled.
HF is a compound of combustion processes. Due to its risks for human health, emissions are monitored continuously.[ 3 ]
Early fire detection technologies rely on highly sensitive detection of carbon monoxide. Coal-fired power plants, steel mills or biomass deposits use these smoke detectors to increase process and workers safety.
Formaldehyde has been used in consumer and industrial products since the beginning of the 19th century. Currently the annual formaldehyde production accounts for 21 million tons. About 50 % are processed as adhesives in pressed wood panels. In 2004 formaldehyde has been classified carcinogenic by the International Agency for Research on Cancer. Since then formaldehyde concentrations have been strictly controlled in the production process as well as in the finished product. Laser-based measurement systems are required to detect the maximum levels of 0.01 ppb (USA) and 2 ppb (EU).[ 143 , 114 , 108 , 78 , 22 , 9 ]
Leaks of CH4 may cause dangerous situations and are hard to locate precisely. Hence, maintenance of underground pipelines produces high costs. CH4 leaks are also an important source for greenhouse gases. With TDLS a strong tool is available to manufacture portable leak detectors.[ 162 ]
H2S occurs as a corrosive, toxic and explosive side product in the petrochemical industry. Continuous monitoring of this hazardous compound is critical to avoid corrosion of natural gas pipelines and ensure workers safety. Real-time analysis is essential to guarantee that burning fuels are H2S clean in order to prevent acid rains.[ 76 , 69 , 3 ]
CO2 is a natural diluent in oil and gas deposits. When it reacts with H2S and H20 steel pipelines corrode. Real-time monitoring of CO2 at natural gas custody transfer points is necessary to avoid contaminated gas from flowing downstream. Immediate measures may be taken to purify the natural gas.[ 115 ]