SUBJECTIVE PERCEPTIONS? HAZARD AND RISK ASSESSMENT
It is important to differentiate between hazard and risk. The former is a measure of the intrinsic properties of a substance while the latter reflects the probability of the hazard being realized. Risks may be individual or societal, voluntary or involuntary and well or poorly quantified. The nature of the risk and the degree of an individual's control over it markedly affects the perception of risk. Thus many people accept a high voluntary, individual risk such as smoking cigarettes, but are not prepared to accept a considerably lower involuntary, societal risk such as living near a nuclear power station. A number of hazardous chemicals may be encountered in buildings but this does not necessarily mean that they pose a significant risk, for example radon is a known hazard in certain parts of the country but in others it is present at such low levels that there is little risk.
For starters, one has to comprehend that hazard and risk are not the same. Other than in case of misuse, they are not interchangeable terms.
Hazard is the innate property of some event (process, activity or substance) to cause harm. Risk on the other hand, brings the question mark, an element of probability into the framework of that event mentioned above. This is actually a chain of events: a complex of two different possibilities: occurring and harm producing. Ideally, the strategy is to break this chain of events, both through design and maintenance.
Risk* is pure probability: the chance that something adverse may happen, the likelihood of a specified (undesired) event occurring within a certain timeframe or in specified circumstances. In other words, risk is a measurable quantity of losing (or not gaining) and is different from uncertainty, which is not measurable. Whenever an activity that involves taking a risk is performed, humans usually do so because people view some benefit that outweighs the potential risk. We also attempt, at least at times, to reduce or eliminate it.
In reality, we also face to varying degrees risks from naturally occurring hazards. Being struck by lightning is a classic example. Because lightning usually kills only rarely, and the risk is very low, we treat it as negligible, i.e. apart from taking some very simple precautions, the possibility of dying in this way does not really influence the behavior of most people. Although the risk of being caught in a flood, mud slide, volcanic eruption or earthquake is probably much higher, most people do not take these risks very seriously either.
A good example is mountaineering (or mountain climbing), the sport of attempting to attain, high points in mountain areas, usually for the pleasure of the climb in itself. For the untrained, mountaineering is a dangerous pastime. Although the term is often loosely applied to walking up low mountains that offer only moderate difficulties, it is more properly restricted to climbing in localities where the terrain and weather conditions present such hazards that, for safety, a certain amount of previous experience will be found necessary. Mountaineering differs from other outdoor sports in that nature alone provides the field of action (and more or less all of the opposition) for the participant. Climbing mountains embodies the thrills produced by testing one's courage, resourcefulness, cunning, strength, ability, and stamina to the utmost in a situation of inherent risk. Mountaineering, to a greater degree than other sports, is a group activity, with each member both supporting and supported by the group's achievement at every stage. For most climbers, the pleasures of mountaineering lie not only in the "conquest" of a peak but also in the physical and spiritual satisfactions brought about through intense personal effort, ever-increasing proficiency, and contact with natural grandeur.
Water constitutes a hazard to construction. The risk element appears whenever something concrete happens: a flood, a mud slide, a crack in the foundation which allows water to penetrate either the structure or the interior space within the building envelope).