Margins of safety

The two levels of NAAQS, primary and secondary, are Hsted in Table 3. Primary standards were set to protect pubHc health within an adequate margin of safety secondary standards, where appHcable, were chosen to protect pubHc welfare, including vegetation. According to the CAA, the scientific bases for the NAAQS are to be reviewed every 5 years so that the NAAQS levels reflect current knowledge. In practice, however, the review cycle takes considerably longer. 

Once a substance is designated by EPA as a ha2ardous air pollutant (HAP), EPA has to promulgate a NESHAP (National Emission Standard for Ha2ardous Air Pollutants), designed to protect pubHc health with an ample margin of safety. 

Of the water-soluble vitamins, intakes of nicotinic acid [59-67-6] on the order of 10 to 30 times the recommended daily allowance (RE)A) have been shown to cause flushing, headache, nausea, and moderate lowering of semm cholesterol with concurrent increases in semm glucose. Toxic levels of foHc acid [59-30-3] are ca 20 mg/d in infants, and probably approach 400 mg/d in adults. The body seems able to tolerate very large intakes of ascorbic acid [50-81-7] (vitamin C) without iH effect, but levels in excess of 9 g/d have been reported to cause increases in urinary oxaHc acid excretion. Urinary and blood uric acid also rise as a result of high intakes of ascorbic acid, and these factors may increase the tendency for formation of kidney or bladder stones. AH other water-soluble vitamins possess an even wider margin of safety and present no practical problem (82). 

State-of-the-Ahi Control. Computer control using feed-forward capabiUty can save 2—20% of a unit s utiUties by reducing the margin of safety (5). Unless the discipline of a controller forces the reduction of the safety margin, operators typically opt for increased safety. Operators are probably correct to do so when a proper set of analy2ers and controllers has not been provided and maintained. 

A reflux reduction of 15% is typical. Improved control achieves this by permitting a reduction in the margin of safety that the operators use to handle changes in feed conditions. The key element is the addition of feed-forward capabiUty, which automatically handles changes in feed flow and composition. One of the reasons for increased use of features such as feed-forward control is the reduced cost of computers and online analy2ers. 

Noscapine [128-62-1] (45) is the second most abundant alkaloid found in opium. Unlike most opium alkaloids, however, it has an isoquinoline rather than a phenanthrene ting system. Noscapine was first isolated in 1817 but its antitussive activity was not demonstrated pharmacologically until 1952 (63). Clinical studies have confirmed its effectiveness. It is not a narcotic and has a wide margin of safety when given orally. Death could be produced in rats only with doses > 800 mg/kg (64). Noscapine is isolated from the water-insoluble residue remaining after processing opium for the manufacture of morphine. 

Breakeven charts can be plotted in any of the three forms shown in Figs. 9-2, 9-3, and 9-4. The abscissa shown as annual sales volume R is also frequently plotted as a percentage of the designed production or sales capacity Rq. In the case of ships, aircraft, etc., it is then called the percentage utilization. The percentage margin of safety is defined as... 

For design, the slip velocity is derated to 70-80 percent of the calculated value to give some margin of safety this sets the design value of the continuous phase velocity (V ). The column cross sectional area (and therefore diameter) is set by QJVc- With the diameter set, the other dimensions can be set using the ratios given above. 

For any proposed suppression system design, it is necessary to ascribe with confidence an effective worst-case suppressed maximum explosion overpressure Pred.max- Provided that the suppressed explosion overpressure is less than the process equipment pressure shoclc resistance and provided further that this projected suppression is achieved with a sufficient margin of safety, explosion protection security is assured. These two criteria are mutually independent, but both must be satisfied if a suppression system is to be deployed to provide industrial explosion protection. 

A large number of parameters are involved in the choice of the corrosion protection system and the provision of the proteetion eurrent these are deseribed elsewhere (see Chapters 6 and 17). In partieular, for new locations of fixed production platforms, a knowledge of, for example, water temperature, oxygen content, conductivity, flow rate, chemical composition, biological activity, and abrasion by sand is useful. Measurements must be carried out at the sea location over a long period, so that an increased margin of safety can be calculated. 

The top curve of overspeed versus time demonstrates that the string will accelerate to 22% overspeed due to expansion of the gas trapped between the valve and expander nozzle ring. However, if an eddy current brake were part of the string, the acceleration of the string would be reduced to 11% overspeed. This would provide an important margin of safety. 

Figure 4.1 The true margin of safety (adapted from Furman, 1981 and Nixon, 1958)...

Notes National primary ambient air quality standards define levels of air quality which the EPA Administrator judges are necessary, with an adequate margin of safety, to protect the public health. National secondary ambient air quality standards define levels of air quality, which the Administrator judges necessary to protect the public welfare from any known or anticipated adverse effects of a pollutant. 

Target Load the acceptable concentration or dose of an air pollutant that provides a reasonable margin of safety below the critical load. The target load should be achievable under existing conditions. 

Maximum Contaminant Level Goal (MCLG) - The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety and are non-enforceable public health goals. 

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