Limit, permissible

Limit permissible fire load to 79 x 10 k or 250 tons of hydrocarbon. 

In addition, it may be necessary to limit permissible upward excursions from the TWA. In practice, concentrations of chemical agents in workplace air fluctuate frequently and to a considerable extent. The amount by which the OEL-TWA may be exceeded for short periods without impairment of health depends upon several factors, such as the nature of the substance, the frequency with which high concentrations occur, and the duration of such periods. 

To estimate the limiting permissible value of the wall heat flux we use the thermal balance equation... 

The inequality (8.83) gives an estimation of the limiting permissible value of heat flux on the wall. 

Any release to the environment of more than 1 pound silver nitrate or 1000 pounds of silver alone should be reported to the National Response Center. To limit the amount silver workers are exposed to during an 8-hour shift for a 40-hour work week, the Occupational Safety and Health Administration (OSHA) has set a legal limit (Permissible Exposure Limit or PEL) of 0.01 milligrams of silver per cubic meter of air (mg/m ) in workroom air. 

If the measurands in a traceability chain are intrinsic attributes of materials, the traceability statement might be expected to limit permissible dissimilarities of matrices. (By an intrinsic attribute of a homogeneous material we mean one that is invariant with respect to sampling). 

If more than 300 citations are found using any form of chemical identification, the references may be enriched in relevance and quality by adding any number of the following characterizations of the desired data to the search strategy short-term threshold limit permissible exposure limit acute toxicity ocular terms inhalation terms dermal terms... 

The exposure limits (permissible exposure limits) set by the Occupational Health an Safety Administration is 0.05 mg m for skin in both general industry and construction industry. This is the same limit (0.05 mgm ) established by ACGIH (TLV) and the National Institute for Occupational Safety and Health (recommended exposure limit). 

The Occupational Safety and Health Administration (OSHA) has set a legal limit (Permissible Exposure Limit, or PEL) of 1 ppm in workroom air to protect workers during an 8-hour shift in a 40-hour workweek. 

Figure 9.8b is a typical plot of the outlet-to-inlet solute concentration in the fluid as a function of time from the start of flow. The resulting S-shaped curve is called the breakthrough curve. At times t, t2, and t3 the exit concentration is practically zero. At time th when the concentration reaches some limiting permissible value, or break point, the flow is stopped or diverted to a fresh sorbent bed. 

For example, in the case of light Arabian crude (Table 8.16), the sulfur content of the heavy gasoline, a potential feedstock for a catalytic reforming unit, is of 0.036 weight per cent while the maximum permissible sulfur content for maintaining catalyst service life is 1 ppm. It is therefore necessary to plan for a desulfurization pretreatment unit. Likewise, the sulfur content of the gas oil cut is 1.39% while the finished diesel motor fuel specification has been set for a maximum limit of 0.2% and 0.05% in 1996 (French specifications). 

Figure 10.15 Schematic showing alternative limits in the plot of KC2/R0 versus sin (0/2) and their interpretation. (Reprinted with permission from H. Benoit, A. M. Holtzer, and P. Doty,/. Phys. Chem. 58 635 (1954), copyright 1954 by the American Chemical Society.]...

Figure 9.32 Isotopic enrichment of SFg by multiphoton dissociation following irradiation in the vibrational band of SFg. The absorption spectrum is shown (a) before and (b) after irradiation. (Reproduced, with permission, from Letokhov, V S., Nature, Land., Ill, 605, 1979 Copyright 1979 Macmillan Journals Limited)...

POLYETTiERS - TETRAHYDROFURAN AND OXETANE POLYTffiRS] (Vol 19) PEL. See Permissible exposure limit. 

Material Safety Data Sheets (MSDS) issued by suppHers of acetone ate requited to be revised within 90 days to include new permissible exposure limits (PEL). Current OSHA PEL (54) and ACGIH threshold limit values (TLV) (55) ate the same, 750 ppm TWA and 1000 ppm STEL. Eot comparison, the ACGIH TWA values for the common mbbing alcohols are ethyl, 1000, and isopropyl, 400 ppm. A report on human experience (56) concluded that exposure to 1000 ppm for an 8-h day produced no effects other than slight, transient irritation of the eyes, nose, and throat. 

Air Contaminants—Permissible Exposure Limit," Title 29 Code of Federal Regulations Part CFR 1910.1000, OSHA, 1989, p. 3112. 

The OSHA permissible exposure limit (11) and the American Conference of Governmental Industrial Hygienists (ACGIH) estabHshed threshold limit value (TLV) (12) for fluorides is 2.5 mg of fluoride per cubic meter of air. This is the TLV—TWA concentration for a normal 8-h work day and a 40-h work week. 

Stannous fluoride is used in dentifrices and dental preparations. The OSHA permissible exposure limit (44) and ACGIH (45) estabUshed TLV for fluoride is 2.5 mg/m of air. 

Handling and Toxicity. Tungsten hexafluoride is irritating and corrosive to the upper and lower airways, eyes, and skin. It is extremely corrosive to the skin, producing bums typical of hydrofluoric acid. The OSHA permissible exposure limits is set as a time-weighted average of 2.5 mg/kg or 0.2 ppm (22). 

Industrial materials without sufficient scaling resistance frequendy fail after a short period of time as a result of rapid oxidation or hot corrosion, in conjunction with severe spalling owing to poor adherence of the scale to the metallic component. As a result, the permissible limits of metal loss often are exceeded and expensive, and premature replacement of parts is requited. Extensive efforts are made to develop alloys which are not simply strong at elevated temperatures but which also possess the adequate surface stabiUty. 

Pressure. Within limits, pressure may have Htfle effect in air-sparged LPO reactors. Consider the case where the pressure is high enough to supply oxygen to the Hquid at a reasonable rate and to maintain the gas holdup relatively low. If pressure is doubled, the concentration of oxygen in the bubbles is approximately doubled and the rate of oxygen deHvery from each bubble is also approximately doubled in the mass-transfer rate-limited zone. The total number of bubbles, however, is approximately halved. The overall effect, therefore, can be small. The optimum pressure is likely to be determined by the permissible maximum gas holdup and/or the desirable maximum vapor load in the vent gas. 

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