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Viewl-TECH® <br />HUMAN RESPONSE to AIRBLAST <br />As demonstrated by a number of studies, there are no physiological health risks associated with <br />airblast overpressures from conventional blasting operations (below 140 dB). As with anything, <br />the level of annoyance is highly subjective from person to person. <br />Observers are more likely to respond unfavorably inside a structure rather than being outside. <br />Moreover, the negative response is increased if the observer is inside his/her own house. The <br />secondary sounds of the house responding are the most noticeable to the observer, such as the <br />rattling of loose doors, windows, panels, and loose objects on shelves, or the sound of the airbiast <br />impacting against the exterior walls or roof. The primary concern of persons who hear the <br />sounds generated by airblast is that of potential damage to their homes, not to their person. <br />FACTORS WHICH AFFECT AIR OVERPRESSURE <br />There aze a number of factors, which affect air overpressures. <br />• Maximum Charge Weight Per Delay <br />As with ground vibration, the maximum chazge weight per delay can be the most important <br />factor when dealing with the cause of airblast overpressure. <br />• Depth of Burial <br />The next criteria in direct correlation with weight of explosive, is the depth of burial of the <br />' explosives. This could either be the depth below the ground surface or the distance behind the <br />open face, although the results are also affected by how strongly and how rapidly the rock <br />moves. <br />• Exposed Surface Detonations <br />' As with the main charges, the exposed surface detonations (detonating cord, surface delays, etc.) <br />tend to generate much sharper noises and could produce higher overpressures than the main <br />buried charges. <br />• Atmospheric Factors <br />The two most important factors, which affect the propagation of air overpressures, aze <br />temperature gradients and wind. <br />I) Temperature Gradients <br />Temperature gradient is explained as the rate of change of the air temperature with <br />distance/altitude. Under normal conditions, the air temperature changes slowly with altitude. <br />The air temperature will decrease 3.5 °F for every 1,000 ft rise above the surface. Furthermore, <br />the velocity of sound in the air is decreased with the increase in altitude. This change in velocity <br />6 <br />