Toxic vapours, detection

Hosseini SH, Oskooei SHA, Entezami AA (2005) Toxic gas and vapour detection by polyanUine gas sensors. Iran Polym J 14(4) 333-344... 

LPG is considered to be non-toxic witli no chronic effects, but the vapour is slightly anaesthetic. In sufficiently high concentrations, resulting in oxygen deficiency, it will result in physical asphyxiation. The gases are colourless and odourless but an odorant or stenching agent (e.g. methyl mercaptan or dimethyl sulphide) is normally added to facilitate detection by smell down to approximately 0.4% by volume in air, i.e. one-fifth of the lower flammable limit. The odorant is not added for specific applications, e.g. cosmetic aerosol propellant. 

BS EN 45544 Electrical apparatus for the direct detection and measurement of toxic gases and vapours ... 

Liquefaction means a volume reduction of approximately 600 times. This corresponds to an energy density that is 600 times higher than natural gas at atmospheric conditions. Since LNG has no odour, leak detection requires special instrumentation. Furthermore, LNG is colourless and non-toxic, and non-carcinogenic. The specific weight of LNG is 45% of water. In vaporised phase - mixed with air - LNG can only ignite if the concentration of gaseous methane is in the range 5-15%. Neither LNG, nor its vapour can explode in an unconfined environment [8],... 

The multiplicity of abiotic transformation products which have been detected for aminocarb has prompted a comparison of the anticholinesterase activity, in vivo insect toxicity and relative volatility of a series of oxidation products. Successive oxidations of the aryldimethylamino group resulted in increased toxicity whereas oxidation of the arylmethyl group or of the carbamate N-methyl group considerably reduced toxicity. Saturated vapour concentrations of the toxic transformation products were only slightly lower than the parent carbamate. 

Maintaining the quality of food is a far more complex problem than the quality assurance of non-food products. Analytical methods are an indispensable monitoring tool for controlling levels of substances essential for health and also of toxic substances, including heavy metals. The usual techniques for detecting elements in food are flame atomic absorption spectroscopy (FAAS), graphite furnace atomic absorption spectrometry (GF AAS), hydride generation atomic absorption spectrometry (HG AAS), cold vapour atomic absorption spectrometry (CV AAS), inductively coupled plasma atomic emission spectrometry (ICP AES), inductively coupled plasma mass spectrometry (ICP MS) and neutron activation analysis (NAA). 

The benefit of sample preparation techniques using microwave acid digestion and bomb combustion is that the sample is totally enclosed during the decomposition. These methods remove matrix interference and generate aqueous solutions, which can be analysed using ICP-OES. Sub-trace concentrations can be detected when hyphenated attachments are used, e.g. ultrasonic nebuliser, hydride generation or continuous cold vapour method. These methods are essential where trace levels of toxic elements are present that need to be identified and quantified. 

UK/DSIR. 1939. Methods for the detection of toxic gases in industry Carbon disulfide vapour. London, England United Kingdom, Department of Scientific and Industrial Research, His Majesty s Stationery Office. Leaflet No. 6. 

The combination of a low TLV with a fairly high vapour pressure and an odour that is difficult to detect make EDC dangerous from the toxicity point of view. 

These are not self-contained units, and extraction of volatiles is achieved by placing in a well-ventilated room or in a fume cupboard. Excellent ventilation and sensing equipment to detect vapour levels in the vicinity of the equipment are essential from the point of view of fire hazard and toxicity. 

Utriainen, M., Karpanoja, E., Paakkanen, H., Combining miniaturized ion mobility spectrometer and metal oxide gas sensor for the fast detection of toxic chemical vapours. Sensors Actuators B, B93, 17-24, 2003. 

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