Failure, hood

The simplest way to cope with such potential hazards is to develop a set of instructions about what to do in case of failures. These could be posted, preferably in a place where they can be read with the emergency light. As soon as a failure occurs, laboratory personnel should immediately turn off all affected equipment. In case of an electrical failure, attention should be paid to samples that may be giving off hazardous fumes from the hood. 

Release of vapor CSM from lab hood and into workplace or atmosphere. 1. Power failure 1. Loss or lab I A 1 hood capture. Release of CSM into workplace. Personnel injury or death. System/fac i1ity damage minimal. None... 

Unfortunately, fumes can drift out of a hood for a variety of reasons and aerosols will drift out. Hoods strain heating and air conditioning systems by consuming vast quantities of room air, they are incompatible with controlled atmospheres, they provide no shielding with the sash up, and their protection is degraded by turbulent flows if they are located near doors or in areas that have heavy pedestrian traffic. Flow at the hood face is obstructed by workers standing in front of the hood and all protection is lost when power failures are experienced. 

Laboratories designed for the handling of toxic materials normally maintain reduced pressures in the rooms and hallways, relative to the pressure outside the buildings. Hoods should therefore be fitted with antibackflow valves to avoid sucking the contents of the ductwork into the laboratory in the event of a power failure. Backup power provided in 15 seconds does not prevent this phenomenon, even if the hoods and airhandlers are designed to restart automatically. 

Power surges or failures may leave the best designed airhandling equipment in various states of disarray. It is valuable in such circumstances to be able to assess the status of the hoods from outside the building. An easy to read status board can be placed so as to be visible from the outside through a window and/or remote outputs can be made available at other locations. Mechanisms for resetting the hoods should also be conveniently located. 

As discussed by Hood and Miller (7), and in the lecture by Hood at the Maternal Toxicology Symposiums in 2009 (summarized in Beyer et al. (8)), it can be argued that it is Khera s interpretation, rather than the developmental toxicity study results themselves, that may be of concern. Khera s literature review indicated a possible association between maternal toxicity and embryo-fetal effects, but it did not establish a causal relationship between these two observations. Additional criticisms of Khera s hypothesis include the fact that his literature review was retrospective, there was a potential selection bias arising from the general tendency not to publish negative data, and the failure to adequately address maternal toxicity endpoints in the published literature of the time. In fact, Khera himself stated that in 40% of the studies he evaluated in support of his hypothesis the maternal toxicity data were insufficient or nonexistent (9). 

Dope-Size Test. It has been recognized that the granulation of the solid ingredients or an expi has an appreciable effect on its expl characteristics a considerable variation might have as much effect as a change in chem compn, and so may cause failure in gallery tests for permissible expls. The "dope-size test" consists of treating a sample of expl (under a hood) with carbon bi-... 

Hood WB, Jr, Dans AL, Guyatt GH, et al. Digitalis for treatment of congestive heart failure in patients in sinus rhythm. Cochrane Database Syst Rev. 2004 CD002901. 

Watson AMD, Hood SG, May CN. 2006. Mechanisms of sympathetic activation in heart failure. Clin Exp Pharmacol Physiol 33 1269-1274. 

Traps are supposed to prevent exhausts from being released into the working environment. However, they should not be relied on to the extent of the possible negligence of the useifs) or other possible accidents causing failure. Therefore, all exhausts from mechanical pumps should be vented to fume hoods (see Fig. 7.14 on exhausting mechanical pumps to fume hoods). 

McAinsh J, Holmes BF, Smith S, Hood D, Warren D. Atenolol kinetics in renal failure. Clin Pharmacol Ther 1980 28(3) 302-9. 

Caution. These preparations involve the handling of chlorine solutions under pressure. Because container failure could release the toxic gas violently, the vessels (if glass) should be heated in an efficient fume hood with good shielding. 

Similarly, the hood status was monitored by a discrete contact closure that was connected to the power circuits of the hood. Thus, a failure of the hood exhaust effectively caused a system interlock by removing power to the AIMS. The NI controller was not connected to one of the affected circuits, so it remained operational. Nonetheless, without power in the AIMS, it could not take further action with the system. 

Assessment of enzyme activity or stability at or above 100° needs considerable care. Spills of water/reaction mixture into oil baths can result in small explosions and sprays of hot oil, and the failure of any closed vessel incubating at these high temperatures can have similar results. Oil baths should be run in fume hoods, with lids raised only for manipulation. Operators should wear lab coats that include cover of the neck area, polycarbonate face shields, and long insulated gloves and should use tongs for handling vessels... 

Work with substantial amounts of materials with hazard ratings of 1 or 2 shall be performed in a hood or in an assembly designed to be safe in the event of a worst-case failure. 

With aU the variation allowed by all of these configurations, the room air supply system must be so designed as to maintain the room air balance, no matter what sash arrangement is used, or for that matter, whether the hoods are in operation or not. The hoods and HVAC systems need to be interlocked to ensure this. In addition, if the HVAC system should fail, the hoods need to be equipped with an alarm to alert users of the failure. The hoods in such a case should be shut down if this not done automatically and the sashes closed to prevent fumes from escaping into the laboratory. In newly built facdities, especially larger ones, the HVAC systems are managed by a computer system to ensure the room air balance is maintained at all times, and so designed as to provide an alarm should the air velocity fall below the specified value in the exhaust ducts. 

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