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A total of 993 mice, rats, guinea pigs and rabbits were exposed to sharp-rising overpressures of various short durations. They were mounted on a concrete pad above which high-explosive charges, ranging in weight from 0.50 oz to 64 lbs, were detonated. Pressure-time measurements were obtained with pencil-type and shock-tube piezo-electric gauges on the pad directly beneath the charges. The duration of the blast waves ranged from 0.40 msec to 6.8 msec. The LD-50 pressures were calculated for each species at the different pulse durations. In general, the pressures required to produce 50-percent lethality rose at the shorter durations. Combining the results of this study with those from previous shock-tube investigations made it possible to define the tolerance of four small-animal species to sharply rising overpressures as a function of pulse duration.
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Experience with animals exposed in a variety of above and below ground structures during full-scale field operations at the Nevada Test Site in 1953, 1955 and 1957 were reviewed. The data were assembled and summarized to illustrate the nature of the blast-induced problems of significance in protective shelters, "open" as well as "closed". Potential hazards were related to the following: various patterns of variation in environmental pressure; translational events associated with transient, high-velocity winds, ground shock and gravity involving the impact of energized inanimate objects on the one hand the the consequences of whole-body displacement on the other; non-line-of-site thermal phenomena including hot objects and rapidly moving hot, dust- laden air and debris; and dust, in the respirable size range, sufficiently high in concentration even in "closed" shelters as to warrant design measures to minimize or eliminate the occurrence of small particulates whether arising from wall spalling or otherwise. Tentative biological criteria, conceived to help assess human hazards from blast-related phenomena, were presented. Relevant data from the literature and on- going research in environmental medicine were set forth to aid the reader in appreciating how the criteria were formulated, what information was extrapolated from animal data, and wherein "best estimates" were employed. "State-of-the-art" concepts were noted to emphasize areas in which more thinking and research must continue if more refined, complete and adequate criteria are to be forthcoming for assessing man's response to blast-induced variation in his immediate environment.
One hundred and eighteen guinea pigs were exposed to air blast in shallow, deep, and deep-with-offset chambers mounted on a shock tube. The LD(50)- 24 hours, in terms of the incident shock pressures measured adjacent to the chambers, was calculated by probit analysis to be 34.9 psi, 19.5 psi, and 26.8 psi for animals in the shallow, deep, and deep-with-offset chambers, respectively. According to the LD(50) incident pressures, the shallow chambers offered the most protection against air blast; the deep chambers, the least. Comparing the LD(50)pressure dose at the animals' location revealed little difference in their tolerance to overpressure, per se; i.e., LD(50) reflected pressures measured by gauges within the deep and deep-with-offset chambers were 34.6 psi and 35.9 psi, respectively. The LD(50) incident shock pressure of 34.9 psi in the shallow chambers was considered to be the dose at the animal's location in that instance. The protection against blast provided by the three chambers and the response of animals to the particular pressure time patterns encountered are discussed.
For personnel standing or prone-side-on to the charge when it is detonated at or near the surface, the side-on incident plus dynamic pressures become the effective pressure; however, with orientations end-on in this situation, only the side-on incident pressure appears to be the maximal effective pressure.