Hazard severity defined

Table IV. Hazard Severity Categories Defined in MIL-STD-882A...

Process risk is defined by the frequency of the occurrence and the potential consequence severity of the process hazard. To define the frequency, the initiating causes (e.g., single causes or multiple causes and conditions) are identified for each process hazard, and their frequency of occurrence is estimated. The consequence severity is the logical conclusion to the propagation of the process hazard if no protection layers are implemented as barriers to the event. 

Hazard severity is defined as the aggregate of the worst credible outcomes of a hazards-related incident, considering the exposure. 

By using a matrix to quantify and prioritize the risks the intrinsic subjective nature of risk assessment is not reduced, but a consistent framework for evaluating risk is provided. Although different matrices may be used for various applications, any risk assessment tool should include the elements of hazard severity and mishap probability. The risk level defined in the matrix represents the degree of risk associated with a hazard by considering these two elements. 

Risk Mathematically, expected loss the probability of an accident multiplied by the quantified consequence of the accident (SSDC) an expression of the possibility of a mishap in terms of hazard severity and hazard probability (MIL-STD-882) note Hazard exposure is sometimes included (AFR 800-16) as defined in NHB 5300.4(10-2), The chance (qualitative) of loss of personnel capability, loss of system, or damage to or loss of equipment or property (NSTS 22254) a measure of both the probability and the consequence of all hazards of an activity or condition. A subjective evaluation of relative failure potential. In insurance, a person or thing insured (ASSE). 

Risk is expressed as an estimate of the probability of a hazard-related incident or exposure occurring and the severity of harm or damage that could result. All risks with which safety and health professionals deal derive from hazards. There are no exceptions. A hazard is defined as the potential for harm. Hazards include all aspects of technology and activity that produce risk. Hazards include the characteristics of things (equipment, dusts, chemicals, etc.) and the actions or inactions of people. 

The ERDEC Safety Office has since performed risk assessments on various detectors brought to government facilities for testing. Such procedures, when followed, permit the return of contaminated items to manufacturers. In the following, assessments of two detectors, the MiniRae and the M43A1 upgrade, are used as examples of how risks were assessed. Tables 3.16 and 3.17 define hazard severity and probability levels used as the criteria for assessing risk. 

A catastrophic hazard is a hazard that has a Category I (Catastrophic) severity level, as defined by the hazard severity criteria in MIL-STD-882. 

A CSI is essentially the same as an SCI except that systems required to identify CSIs have additional statutory and regulatory requirements that the contractor must meet in supplying those CSIs to the government. For systems required to have a CSI list, HA and mishap risk assessment is used to develop that list. The determining factor in CSIs is the consequence of failure, not the probability that the failure or consequence would occur. CSIs include items determined to be life-limited, fracture critical, fatigue-sensitive, and so on. Unsafe conditions relate to hazard severity categories I and II of MIL-STD-882. A CSI is also identified as a part, subassembly, assembly, subsystem, installation equipment, or support equipment for a system that contains a characteristic, failure mode, malfunction, or absence of which could result in a Class A or Class B accident as defined by DoDINST 6055.7. 

The HRI matrix is a risk matrix that is utilized to establish the relative (vice absolute) risk of a hazard. The matrix maps hazard severity on one axis and hazard likelihood on the other axis. Once a hazard s severity and likelihood are determined, they are mapped to a particular HRI matrix cell (the likelihood-severity intersection), which yields the HRI risk level for that hazard. The likelihood and severity axes are broken into cells defined by qualitative and semiquantitative criteria. 

One method for measuring and ranking the severity of a hazard is to establish different hazard severity levels, with each level having an increasing amount of severity. MIL-STD-882 categorizes hazards into four severity levels, which are defined as follows ... 

Mishap risk—a safety metric characterizing the amount of danger presented by a potential mishap, where the likelihood of the mishap s occurrence is combined with the resulting severity of the mishap. Mishap risk likelihood defines the likelihood of the mishap occurring, while mishap risk severity defines the expected final consequences and loss outcome expected from the mishap event. The mishap likelihood and severity can only be computed from the information contained in the hazard description. 

The hazards and risks associated with work activities need to be identified first. Hazards are defined as situations with the potential to cause harm or loss. Under the CDM Regulations it is both hazardous circumstances and hazardous activities that potentially threaten the health and safety of employees. So the identification of hazards and activities is an essential part of analysing the risks that these represent to health and safety in the workplace. Risk is a function of three factors the likelihood of actual harm resulting from a hazard, the potential severity of the consequence should it occur, and the number of people that might be exposed to the harm. There are a number of well established methods by which risks may be quantified and hazard indices developed, if reliable data is available. Risk is normally measured in terms of the probability of a worker being injured in any given year, while carrying out his or her work, by the severity of injury suffered. Accident frequency is often used as the prime indicator of risk overall. 

The combination of the hazard severity and the hazard probability defines the hazard risk classes. These classes are listed in Table 4 with different levels of tolerability Class A forms the intolerable area of the risk matrix, Class B and C the tolerable area and class D means acceptable risk. 

Previous issues of MIL-STD-882 used the term hazard (defined as a condition that is a prerequisite to a mishap , and went on to define hazard severity and hazard probability levels (see Tables B.13 and B.14). This was definitively incorrect, as these categories described accidents (or mishaps) - not hazards. 

Risk is defined as an expression of possible loss over a specific period of time or number of operational cycles. It may be expressed as the product of hazard severity and hazard probability. 

There are several formal lists of carcinogens. Thus, in the UK under the Control of Substances Hazardous to Health Regulations 1999 (see later) carcinogens are defined as ... 

The risk evaluation process defines the equipment, hazards, and events leading to an accident. It detennines the probability tliat an accident will occur. The severity and acceptability of the risk are also evaluated. 

Tlie reader should also note that tlie risk to people can be defined in terms of injury or fatality. The use of injuries as a basis of risk evaluation may be less disturbing tlian tlie use of fatalities. However, tliis introduces problems associated with degree of injury and comparability between different types of injuries. Further complications am arise in a risk assessment when dealing witli multiple hazards. For example, how are second-degree bums, fragment injuries, and injuries due to toxic gas e.xposure combined Even where only one type of effect (e.g., tlueshold to.xic exposure) is being evaluated, different durations of e.xposure can markedly affect tlie severity of injury. 

Bioavailability is defined as the portion or fraction of a chemical that is available for biological action and is influenced by several factors including the molecular size and charge of a molecule, structural features of membranes, first pass metabolism, and therefore, bio availability can be influenced by the molecular structure of a chemical. This situation presents an opportunity for molecular designers to manipulate a chemical s structure to decrease bioavailability and consequently hazard. If the availability of a molecule can be decreased, the amount of chemical at the site of action is decreased which leads to decreased toxicity. 

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