Safe exposure time

Buettner, K. "Heat Transfer and Safe Exposure Time for Man in Extreme Thermal Environment." ASME paper 57-SA-20. Proceedings of the Heat Transfer Division ASME Semi-Annual Meeting, San Francisco, CA, June... 

Liquid sterilants are known to corrode the metal parts of articles and instmments that are to be sterilized, although articles composed exclusively of glass or certain type of corrosion-resistant metal alloys can be safely processed. Because the degree of corrosion is related to length of exposure, many articles are merely disinfected in a shorter exposure time. Disinfection may be suitable for certain appHcations. The safety of using Hquid sterilants must be judged by a qualified microbiologist. 

Safe Exposure Levels. The U.S. Occupational Safety and Health Administration (OSHA) has adopted workplace exposure limits designed to keep airborne concentrations weU below the levels known to cause health problems (35) including ( ) daUy time-weighted average (TWA) exposure over an eight-hour day is not to exceed beryUium concentrations of 2 lg/m of air and (2) short-term exposure should not exceed beryUium concentrations of 25... 

Tests have been outlined for each exposure category to assure safe use of the time period designated. The tests for each exposure category assure the safe use of the new pharmaceutical excipient for the time frame specified for the specific exposure category. Additional tests are required for longer exposure times. 

Process the paper with the safelights off and evaluate the test. Find the exposure time of the area that first shows the ruler s shadow. You will be safe to use the safelight for about one-half of the safelight exposure time that produced the ruler s shadow. 

The prospects of more modern ECT being safe are nil. The newer methods add the risk of anesthesia, often complicated by multiple psychiatric drugs administered simultaneously. The electrical trauma must be sufficient to cause a grand mal seizure. Grand mal seizures, when repeated and especially when as severe as those caused by ECT, are in themselves harmful to the brain. Nor are modern variations in current intensity necessarily more benign because, in order to cause a seizure with the weaker currents, exposure time is often increased by 10-fold or more over earlier ECT methods. Also, in order to overcome the anticon-vulsive effects of the sedatives administered to put the patients to sleep, modern ECT often inflicts more intense electrical energy on the brain than the older animal studies and older forms of ECT (see the section Modified ECT ). Perhaps most obvious and important, the study by Sackeim et al. (2007) shows that the effects of modern ECT continue to be devastating. 

Absorption of US by a medium invariably increases its temperature. Those materials that possess high US absorption coefficients (e.g. bone) experience severe thermal effects compared with, for example, muscle tissue, which has a low absorption coefficient. The increase in temperature upon US exposure at a given frequency varies directly with the US intensity and exposure time. The absorption coefficient of a medium increases with increasing US frequency and so does the temperature as a result. In this context, the time threshold (TT) indicates the time after which a threshold temperature rise is exceeded and hence how long a piece of tissue can be safely exposed to US provided the safe TT is known. 

Although the CW agents and TICs are very toxic, various federal agencies have developed guidelines for possible exposures to determine safe concentrations and times for various operations for each chemical. These are based on work and exposures civilians and mihtary personnel may be required to experience in a toxic environment. There are different exposure times for various activities and therefore for various agencies. Eor example, the Occupational Safety and Health Administration (OSHA) sets permissible exposure levels (PELs) for people who might be exposed... 

A 1945 edition of the Journal of Industrial Hygiene reporting on the first large scale survey of asbestos insulation workers which concluded that Navy shipyard workers involved in the asbestos covering of vessels was a relatively safe operation . That study was criticized, however, because of the relatively short exposure time experienced by the survey workers. 

TLV-STEL Threshold limit value, short-term exposure hmit is the maximum concentration averaged over a 15-min period to which healthy adults can be exposed safely. Exposures should not occur more than four times a day, and there should be at least 60 min between exposmes. 

Recommended noise thresholds in the worlqtlace have been estabUshed by the American Conference of Government Industrial Hygenists. Some examples of the maximum safe levels for different daily exposure times are given below. 

Monopolar current returns to the ESU through the dispersive electrode. If the contact area of the dispersive electrode is large and the current exposure time short, then the skin temperature under the electrode does not rise above 45 C, which has been shown to be the maximum safe temperature [4]. However, to include a safety margin, the skin temperature should not rise more than 6°C above the normal surface temperature of 29-33 C [5j. The current density at any point under the dispersive electrode has to be significantly below the recognized burn threshold of 100 mA/cm for 10 s. This means that the contact area between the electrode and the patient is the most important factor in preventing a dispersive electrode burn. 

Supercritical fluid extraction is another method used in PHA recovery. Supercritical carbon dioxide is widely used, due to its high solubility with other compounds. It is safe (low toxicity and reactivity) and convenient to use. Furthermore, supercritical fluids possess the unique properties of high densities and low viscosities, making them a suitable choice of solvent for extraction. The efficiency of this extraction method is highly dependent on the optimisation of the operating parameters, such as temperature, pressure, modifier as well as the exposure times [8]. 

In most quantitative risk analysis methods (Uijt de Haag 2006, purple book 1999), persons present in the hazardous area are assumed to be exposed for a fixed amount of time. Assumptions for fixed exposure times are 30 minutes for a toxic exposure and 20 seconds for exposure to heat radiation. Furthermore, persons are assumed to stay on the same place. The reahty is different in case of an emergency, every person capable of escape will try to rescue himself. In case of a toxic release it is possible that a safe location (for example inside a building) is reached within the prescribed 30 minutes. On the other hand, in case of fire in crowded places, it can be expected that people are unable to escape within 20 seconds. 

A device (instrument or material) used to measure an individual s exposure to a hazardous environment, particularly when the hazard is cumulative over long intervals of time or a selected period of time. They are typically employed to measure sound, radiation, ultraviolet light, or electromagnetic fields to determine if recommended safe exposure limits are being maintained or exceeded. 

Mesothelioma is a malignant tumour of the lining of the lung (pleura) or abdomen (peritoneum). The abdominal form is less common. The disease is significantly related to exposure to asbestos, especially the blue and brown varieties. However, in some 10-15% of cases there is no such history of exposure . Those at risk are miners, manufacturers of asbestos, builders and demolition workers, and even residents in the neighbourhood of blue asbestos working. While the exposure time may have been only minimal, there is no safe threshold of dose below which there is no risk of asbestos related disease. The onset of the disease is delayed, often by some 20 to 50 years. It affects men and women, but the attack rate of the tumour in the exposed population is only about 5%. 

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