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H2S is encountered in the chemical industry in the performance analyses, production of sulphur, sulphuric acid, plastics & dyes and with fertiliser & detergent raw materials. H2S is emitted in the petroleum industry in the production, transportation and processing of oil & natural gas. It is produced in the paper industry when making cellulose, in the rubber industry, coal powered fire stations, sewage treatment plants and waste disposal facilities.
Chlorine (Cl2) is a toxic, corrosive and oxidant liquefied gas. In appearance, it is greenish-yellow, a heavy gas with a suffocating odour. On its own it is non-combustible in air, but most combustible materials will burn in chlorine as they do in oxygen; flammable gases and vapours will form explosive mixtures with chlorine. It reacts explosively, or forms explosive compounds with many common chemicals, especially acetylene, turpentine, ether, ammonia gas, fuel gas, hydrocarbons and hydrogen.
Chlorine has a Threshold Limit Value (TLV – 8-hour exposure) or Time Weighted Average (TWA) of 0.5ppm and its toxic dose level is 15ppm (human inhalation). The recommended detection range is 0-5ppm. Typical applications in which chlorine is used are water treatment, bleaching (paper & textiles), plastics, refining of certain metals, oxidant and as a de-odouriser.
Sulphur Dioxide (SO2) is a toxic, corrosive, liquefied gas, which is produced as a by-product of many industrial processes. In appearance it is a colourless, inflammable gas with a strong suffocating odour. It has a TLV of 2ppm and a recommended detection range of 0-20ppm. The physiological effects of SO2 on industrial workers are comparatively well known with concentrations as low as 2ppm causing eye, nose, throat and upper respiratory tract irritation. This becomes significant at levels of 10ppm and over.
Typical applications are in the smelting, bleaching, preservative, power industry etc. SO2 is also a prime factor in the production of acid rain and the subsequent damage to the world's environment.