Limits of Concentration (of Toxic Gases)
Limits of Concentration (of Toxic Gases) : Limits of concentration of toxic gases are functions of time and concentration, and are related to the effect produced. Thus a concentration which is safe for a short exposure may be lethal for a longer exposure. The limits are expressed in several ways according to the purpose for which they are to be used. The Maximum Allowable Concentration (M. A. C). is used in health and factory legislation to denote the maximum concentration which is permissible for a continuing exposure of an average working day. Lethal concentrations are generally expressed as the "Lethal Dose for 50 per cent effect (LD50) and are the concentrations which will produce a 50 per cent kill, or injury as the case may be, with the stated exposure time. Threshold value is the minimum concentration of a toxic or noxious gas which produces a certain effect such as perception or discomfort. Comparison of these with dangerous concentrations provides an indication of hazards likely to be associated with gases or vapours
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