The hazards

The hazard of an explosion should in general be minimized by avoiding flammable gas-air mixtures in the process. Again, this can... 

The third of the major hazards and the one with the greatest disaster potential is the release of toxic chemicals. The hazard posed by toxic release depends not only on the chemical species but also on the conditions of exposure. The high disaster potential from toxic release arises in situations where large numbers of people are briefly exposed to high concentrations of toxic material, i.e., acute exposure. However, the long-term health risks associated with prolonged exposure at low concentrations, i.e., chronic exposure, also present serious hazards. 

The best way to deal with a hazard in a flowsheet is to remove it completely. The provision of safety systems to control the hazard is much less satisfactory. One of the principal approaches to making a process inherently safe is to limit the inventory of hazardous material, called intensification of hazardous material. The inventories we wish to avoid most of all are flashing flammable liquids or flashing toxic liquids. 

On the other hand, if the hazard is toxicity, process alternatives can be compared by assessing the mass of toxic material that would enter the vapor phase on release from containment, weighting the components according to their lethal concentration. 

What you don t have, can t leak. If we could design our plants so that they use safer raw materials and intermediates, or not so much of the hazardous ones, or use the hazardous ones at lower temperatures and pressures or diluted with inert materials, then many problems later in the design could be avoided. 

At present, all over the world the X-ray television systems, instruments based on magnetic heat and eddy-current methods are used to check the air-passengers luggage and to check staff when entering the hazardous objects. In banks, security services and etc. the optic-television and endoscopic technical vision systems are widely used. 

The preliminary observations underline the manufacturer s responsibilities. He is obliged to analyse the hazards in order to identify those which apply to his equipment. He must design, manufacture and check his equipment to ensure its safety even with respect to their use under reasonably foreseeable conditions. In addition, the manufacturer must interpret and apply the essential requirements in such a way as to take account of the state-of-the-art at the time of design. That latter requirement underlines the evolutive character of the essential requirements which is inherent in the new approach. 

Wider passages are provided for vapours and the comparatively narrow tubes, which are usually fitted through holes bored in cork or rubber stoppers, are absent this considerably diminishes danger in violent reactions and also tends to give better results in distillation under reduced pressure as well as diminishing the hazard of choking. ... 

The hazards of working with diisopropyl ether are de scribed in the Journal of Chemical Education p 469 (1963)... 

The bacterial reduction of Cr(VI) to Cr(III) discussed above is also being used to reduce the hazards of chromium in soils and water (104). 

Silica. SiHca (qv) comes in various forms including quartz [14808-60-7]. It has found wide use as an abrasive in the past, particularly as an inexpensive coated abrasive for woodworking. The term sandpaper is stiU used as a generic term for coated abrasives in many quarters although the use of sand in coated abrasives has been almost entirely elkninated because of the hazard of siHcosis to the user and its inferior grinding properties (especially for metals). 

Acrolein, acrylamide, hydroxyalkyl acrylates, and other functional derivatives can be more hazardous from a health standpoint than acryhc acid and its simple alkyl esters. Furthermore, some derivatives, such as the alkyl 2-chloroacrylates, are powerful vesicants and can cause serious eye injuries. Thus, although the hazards of acryhc acid and the normal alkyl acrylates are moderate and they can be handled safely with ordinary care to industrial hygiene, this should not be assumed to be the case for compounds with chemically different functional groups (see Industrial hygiene Plant safety Toxicology). 

The hazard posed can be limited by maintaining a zone free of people and property around a storage area of explosive material. The minimum radius of the zone depends on the type and quantity of explosive, the extent and type of barrica ding, and the magnitude of loss that would be encountered if an explosive incident occurred. The maximum distance to which hazardous explosive effects propagate depends on the blast overpressure created, which as a first approximation is a function of the cube root of the explosive weight, W. This is termed the quantity distance and is defined as... 

Iodine pentafluoride is an easily storable Hquid source of fluorine having Httie of the hazards associated with other fluorine sources. It is used as a selective fluorinating agent for organic compounds. For example, it adds iodine and fluorine to tetrafluoroethylene in a commercial process to produce a usefiil telomer (124). 

The hazards associated with any faciUty which produces or uses chemicals can be quite numerous, perhaps ia the hundreds or thousands for larger facihties. These hazards are the result of the physical properties of the materials, the operating conditions, the procedures, or the design, to name a few. Most of the hazards are continually present ia a faciUty. 

The purpose of hazard analysis and risk assessment ia the chemical process industry is to (/) characterize the hazards associated with a chemical facihty (2) determine how these hazards can result in an accident, and (J) determine the risk, ie, the probabiUty and the consequence of these hazards. The complete procedure is shown in Figure 1 (see also Industrial hygiene Plant safety). 

The next step is to identify the hazards. This is done using a number of estabUshed procedures. It is not unusual for several hundred hazards to be identified for a reasonably complex process. 

The subsequent step is to identify the various scenarios which could cause loss of control of the hazard and result in an accident. This is perhaps the most difficult step in the procedure. Many accidents have been the result of improper characterization of the accident scenarios. For a reasonably complex chemical process, there might exist dozens, or even hundreds, of scenarios for each hazard. The essential part of the analysis is to select the scenarios which are deemed credible and worst case. 

The hazard analysis and risk assessment procedure can be appHed at any stage in the lifetime of a process or procedure including research and... 

There are a large number of standard methods suitable for each stage in the hazard analysis and risk assessment procedure. The selection of the proper method depends on several factors. Some of these are the type of process, the stage in the lifetime of the process, the experience and capabiUties of the participants, and the step in the procedure that is being examined. Information regarding the selection of the proper procedure is available in an excellent and comprehensive reference (1). 

Hazard analysis does have limitations. First, there can never be a guarantee that the method has identified all of the hazards, accident scenarios, and consequences. Second, the method is very sensitive to the assumptions made by the analysts prior to beginning the procedure. A different set of analysts might well lead to a different result. Third, the procedure is sensitive to the experience of the participants. Finally, the results are sometimes difficult to interpret and manage. 

The hazards checklist usually has three columns next to each item on the Hst. Items can number in the hundreds or even the thousands. The first check is marked if the issue has been considered and complete. The second check is marked if additional consideration or work is required, and the last check is marked if the item does not apply. An example of a detailed checklist can be found in the Hterature (2). 

Hazard and Operability Analysis. The hazard and operabihty analysis (HAZOP) procedure is quite popular because of its ease of use, the abihty to organize and stmcture the information, minimal dependence on the experience of the analysts, and the high level of results. Furthermore, the approach is capable of finding hazards associated with the operation of a faciUty, hence the incorporation of the word operabihty in the name. 

An important part of hazard analysis and risk assessment is the identification of the scenario, or design basis by which hazards result in accidents. Hazards are constandy present in any chemical faciUty. It is the scenario, or sequence of initiating and propagating events, which makes the hazard result in an accident. Many accidents have been the result of an improper identification of the scenario. 

The remaining step in the hazard identification and risk assessment procedure shown in Figure 1 is to decide on risk acceptance. For this step, few resources are available and analysts are left basically by themselves. Some companies have formal risk acceptance criteria. Most companies, however, use the results on a relative basis. That is, the results are compared to another process or processes where hazards and risks are weU-characterized. 

If the hazards and/or risk are unacceptable, then something must be done to change them. The process can be modified, the raw materials changed, and/or the process relocated, for example. In extreme cases, the process might be abandoned as too hazardous. 

A more recent concept which could have significant impact on future designs is that of inherent safety (12). This basic principle states that what is not there cannot be blown up or leak into the environment. Thus, the idea is to avoid the hazard in the first place. 

A partial Hst of the hazards or conditions arising from the workplace (see also Plant safety) and with which industrial hygienists are concerned includes... 

Occupational Safety and Health J ct. OSHA regulations deal principally with physical aspects of safety and those things generally associated with accident prevention. These federal regulations deal especially with the need for estabHshed material safety data sheets and the proper labeling of printing inks under the Hazard Communication Laws. 

The hazards of human poisoning by the parathions have stimulated the development of safer analogues. Two chlorinated derivatives have gready reduced mammalian toxicides. Dicapthon [2463-84-5], 0,0-dimethyl 0-(2-chloro-4-nitrophenyl) phosphorothioate (63) (mp 53°C), has rat LD qS of 400, 330 (oral) and 790, 1250 (dermal) mg/kg. Chlorthion [500-20-8], 0,0-dimethyl 0-(3-chloro-4-nitrophenyl) phosphorothioate (64) (mp 21°C, <71.437), has rat LD qS of 890, 980 (oral) and 4500, 4100 (dermal) mg/kg. These compounds have been used as household insecticides. 

Maleic Acid. Maleic acid is produced by the hydration of maleic anhydride. The hazards of its use ate analogous to those of maleic anhydride. 

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