Exhaust laboratory

Cohen, J.T. and Nikula, K. (1999) The health effects of diesel exhaust laboratory and Epidemiologic Studies,... 

Cocaine is metabolized and eliminated rapidly. The elimination half-life of cocaine is approximately 1 hour, and the duration of effect is very short. The short duration of effect provides a powerful incentive for repeated use of the drug. Many users experience intense drug use cycling, sometimes lasting days, characterized by rapidly repeating doses of cocaine until their supply is exhausted. Laboratory monkeys, given a choice between food and cocaine around the clock for 8 days, consistently choose cocaine. ... 

Nickel carbonyl should be used in totally enclosed systems or under good local exhaust. Plants and laboratories where nickel carbonyl is used should make use of air-monitoring devices, alarms should be present in case of accidental leakage, and appropriate personal respiratory protective devices should be readily available for emergency uses. Monitoring of urinary nickel levels is useful to help determine the severity of exposure and identify appropriate treatment measures. Some large-scale users of nickel carbonyl maintain a supply of sodium diethyldithiocarbamate, or Antabuse, a therapeutic agent, on hand for use in case of overexposure. 

Plutonium solutions that have a low activity (<3.7 x 10 Bq (1 mCi) or 10 mg of Pu) and that do not produce aerosols can be handled safely by a trained radiochemist in a laboratory fume hood with face velocity 125—150 linear feet per minute (38—45 m/min). Larger amounts of solutions, solutions that may produce aerosols, and plutonium compounds that are not air-sensitive are handled in glove boxes that ate maintained at a slight negative pressure, ca 0.1 kPa (0.001 atm, more precisely measured as 1.0—1.2 cm (0.35—0.50 in.) differential pressure on a water column) with respect to the surrounding laboratory pressure (176,179—181). This air is exhausted through high efficiency particulate (HEPA) filters. 

B. A. D AHeva, Procedure and Chartsfor Estimating Exhaust Gas Quantities and Composition, General Motors Laboratory Report 372, Warren, Mich.,... 

With many natural substances also, the exact nature of the corrosive is uncertain and is subject to changes not readily controlled in the laboratory. In other cases, the corrosiveness of the solution may be influenced greatly by or even may be due principally to a constituent present in such minute proportions that the mass available in the hm-ited volume of corrosive solution that could be used in a laboratory setup would be exhausted by the corrosion reaction early in the test, and consequently the results over a longer period of time woiild be misleading. 

By its nature, the present treatment is not exhaustive, nor do we claim that any of the methods taken from the literature are the best possible. Nevertheless, we feel that the information contained in this book is likely to be helpful to a wide range of laboratory workers, including physical and inorganic chemists, research students, biochemists, and biologists. We hope that it will also be of use, although perhaps to only a limited extent, to experienced organic chemists. 

Please notice that in a well-ventilated laboratory and a pressure cell, these experiments can be executed safely. In seven years of graduate research activity at the Chemical Engineering Department of the University of Akron, only one catalyst ignition and one real CO alarm occurred. Several false CO alarms were sounded until someone noticed that they always happened about 2 30 PM. As it turned out, one maintenance employee parked his old car right in front of the air intake to the lab ventilation. He warmed up his car for a while before he started to go home after his shift, and the motor exhaust gas set off the false alarms. 

Wilson, D, J., and B. K. Lamb. 1994. Dispersion of exhaust gases from roof-level stacks and vents on a laboratory building. Atmospheric Environment, vol. 28, pp. 3099-3111. 

This latter equation can also be used for systems without a local exhaust hood by setting the capture efficiency to zero. It could also be used to show the result of recirculation from, e.g., a laboratory fume hood with immediate recirculation. In such a hood all contaminants are generated within the hood and usually also all generated contaminants are captured, so the capture efficiency is 1. The equation demonstrates that if the... 

Specitic hoods Basic openings, nm exhausts, [.VHV, Booths, laboratory fume... 

Certain operations require that the workspace be at a lower pressure than surrounding workspaces, e.g., radioisotope laboratories. In these cases, the exhaust flow rate should exceed the supply flow rate, but this excess should he within 10%. The additional resistance resulting from this imbalance should be considered in the design of the exhaust system, specifically in the selection of exhaust fans. 

For small-scale laboratory work, the exhaust surface is often made as a separate section added to the side of a table or put into a large hole in a table. These tables usually have a sheet metal surface that is resistant to the chemicals used and is easily cleaned. Many circular holes are cut into the metal surface to allow for airflow. This perforation makes the pressure difference over the table quite high and at the same time gives an even distribution of the airflow over the entire surface. These types of exhaust surfaces could be formed to suit different working conditions, e.g., the surface could be made to fit into a sink or to be placed below and around a balance. Using side walls that are not too high, on three or four sides, transforms the table to a partial enclosure, which increases... 

Variable Air Volume Fume Cupboards This type of cupboard incorporates a variable air volume (VAV) controller that regulates the amount of air exhausted from the cupboard such that the face velocity remains essentially constant irrespective of the sash position. A sensor detects either the sash position, the pressure differential l>etween the fume cupboard interior and the room, or the vekxity at some point in the cupboard. This information is used to control either the exhaust fan speed or the position of a control damper. The supply air volume flow rate into the laboratory or workspace should also be regulated. It should be remembered that with the sash in the closed position the amount of air to dilute contaminants in both the fume cupboard and the laboratory is reduced and that there could, for example, be difficulty in reducing contaminant levels below the lower exphasive level. 

The Uniform Fire Code requires that pyrophoric, flammable, or highly toxic gases be within ventilated gas cabinets, laboratory fume hoods, or exhausted enclosures. ... 

For workbenches or laboratory fume hoods with auxiliary supply it is the working person w ho could break the shielding curtain, and in that way contaminants are transported from the interior of the exhaust hood to the space where the person is situated. 

An unducted Class IIA BSC should not be used for work involving hazardous or toxic gases and vapors. The buildup ot chemical vapors in the cabinet by recirculated air) and in the laboratory (from exhaust air) could create health and safety hazards. 

Type B1 cabinets must be hard-ducted, preferably to their own dedicated exhaust system, or to a properly designed laboratory building exhaust. Blowers on laboratory exhaust systems should be located at the terminal end of the duct work. A failure in the building exhaust system may not be apparent to the user, as the supply blowers in the cabinet will continue to operate. A pressure-dependent monitor should be installed to sound an alarm and shut off the BSC supply fan, should failure in exhaust airflow occur. Since this feature is not supplied by all cabinet manufacturers, it is prudent to install a sensor in the exhaust system as necessary. To maintain critical operations, laboratories using Type B1 BSCs should connect the exhaust blow er to the emergency power supply. 

Different protection factors have been defined. One method is to define it as the ratio of the concentration of a contaminant in the exhaust duct (CJ to the concentration in the breathing zone (C[,) of a person standing in front of the enclosure, for example, a laboratory fume hood ... 

The initial solution to this problem was to install an exhaust channel on the opening tor the films, as in Fig. 12. 8. Laboratory experiments show that the principle is inexpedient and it is possible only to obtain a capture efficiency of 70% at a flow rate of 100 m- h"L... 

FIGURE 12.39 (o) Vortex exhaust at a concrete element factory, h laboratory model of the vortex exhaust, and (c) stmpIKIed model of the exhaust. 

For a new process plant, calculations can be carried out using the heat release and plume flow rate equations outlined in Table 13.16 from a paper by Bender. For the theory to he valid, the hood must he more than two source diameters (or widths for line sources) above the source, and the temperature difference must be less than 110 °C. Experimental results have also been obtained for the case of hood plume eccentricity. These results account for cross drafts which occur within most industrial buildings. The physical and chemical characteristics of the fume and the fume loadings are obtained from published or available data of similar installations or established through laboratory or pilot-plant scale tests. - If exhaust volume requirements must he established accurately, small scale modeling can he used to augment and calibrate the analytical approach. 

Davis, D. D.,Jr, G. L. Stevens,Jr., D. Moore, and G. M. Stokes, Theoretical and Measured Attenuation of Mufflers at Room Temperature without How, with Comments on Engine— Exhaust MufQer Design, Technical Note 2893, Langley Aeronautical Laboratory, National Advisory Committee For Aeronautics, Washington, D.C., Feb. (1953). 

The duration of a particular test is likely to be determined by practical factors such as the need for some information within a particular limit of time, or the nature of the operation or process with which the test is concerned. Tests are rarely run too long however, this can happen, particularly in laboratory tests where the nature of the corrosive environment may be changed drastically by the exhaustion of some important constituent initially present in small concentration, or by the accumulation of reaction products that may either stifle or accelerate further attack. In either case, the corrosivity of the environment may be altered considerably. Gross errors may result from the assumption that the results apply to the original conditions of the test rather than to some uncertain and continually changing conditions that may exist during the course of too extended a test period. 

Volume of testing solution If exhaustion of corrosive constituents that may be present in minute concentrations and the accumulation of reaction products which may either accelerate or stifle further attack are to be avoided, the volume or mass of testing solution must be sufficiently large to avoid effects caused by these factors. In laboratory tests, however, practical considerations limit the volume of testing solution that can be provided for. A minimum of 250 ml of testing solution for each 6 - 3 cm of specimen area is suggested in NACE TM0169-76. 

Gas-liquid chromatography (GLC) finds many applications outside the chemistry laboratory. If you ve ever had an emissions test on the exhaust system of your car, GLC was almost certainly the analytical method used. Pollutants such as carbon monoxide and unbumed hydrocarbons appear as peaks on a graph such as that shown in Figure 1.7. A computer determines the areas under these peaks, which are proportional to the concentrations of pollutants, and prints out a series of numbers that tells the inspector whether your car passed or failed the test. Many of the techniques used to test people lor drugs (marijuana, cocaine, and others) or alcohol also make use of gas-liquid chromatography. 

A number of ion-selective electrodes are available from laboratory supply houses whilst not intended to be an exhaustive list, Table 15.3 serves to indicate the variety of determinations for which electrodes are available. An indication is also given of the lower limit of detection of the electrodes this figure may vary somewhat according to the source of the electrode but full details are furnished by the manufacturer of the effective range of use of each electrode and of likely interferences. 

Ensure that the laboratory in which the apparatus is housed is well ventilated and is provided with an adequate exhaust system having air-tight joints on the discharge side some organic solvents, especially those containing chlorine, give toxic products in a flame. 

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