Investigations Explosions

Searching a crime scene is a complex process (25), involving poHce, crime scene technicians, and forensic scientists. The procedure requires careful documentation, collection, and preservation of the evidence. Trace evidence (26) in criminal investigations typically consists of hairs (27,28) both natural and synthetic fibers (qv) (29,30), fabrics glass (qv) (31,32) plastics (33) sod plant material budding material such as cement (qv), paint (qv), stucco, wood (qv), etc (34), flammable fluid residues (35,36), eg, in arson investigations explosive residues, eg, from bombings (37,38) (see Explosives and propellents), and so on. 

Trace or ultratrace and residue analyses are widely used throughout chemical technology. Areas of environmental investigations, explosives, food, pharmaceuticals, and biotechnology rely particularly on these methodologies. 

F. L. Roder, Preliminary feasibihty investigation — explosives detection by dual-energy computerized tomography, The Aerospace Corporation, El Segundo, CA, ATR-78(3860-06)-IND. Security Intelligence Report, Micro-dose finds objects under clothes, 11 March (1991) 3. Aviation Week Space Technology, Personnel scanner, 10 June (1991) 11. 

Investigated explosives included 2,4,6-trinitrotoluene (TNT), 2,4,6,N-tetranitro-N-methylaniline (tetryl), l,3,5-trinitro-l,3,5-triazacyclohexane (RDX), 1,3,5,7-tetranitro-l,3,5,7-tetrazacyclooctane (HMX) and pentaerythritol tetranitrate (PETN). The temperature of the injector, cooled with liquid CO2, was —5°C for 0.3 min, programmed from —5 to 250° C, at a rate of 200°C/min, with a final hold time of 8.4 min. The column temperature was 80° C for 2 min, programmed to 250° C at 25°C/min, with a final hold of 2 min. Electron ionization (El) in the positive-ion mode was used. Figure 4 shows the mass chromatograms of a mixture of explosives (lOppb each), extracted from water by Hquid—liquid extraction and X 100 concentration. Identification was based on typical fragment ions for each one of the explosives. 

Manson Ferrie (Ref 6) investigated explosive mixtures consisting of combustible hydrocarbons such as C2H2, and natural gas with oxygen as oxidizer. 

The OSHA standards are based on the 1970 version of NFPA 495 and differ in some respects from the current version. However, they sfrU require stringent safety precautions which must be followed by any research facility employing or investigating explosive materials. In consequence, any acquisition of explosive materials should be internally reviewed to ensure the abihty on the part of the intended recipient to provide adequate facilities and safeguards to comply with the standards. 

George H. Pimbley, Allen L. Bowman, Wayne P. Fox, James D. Kershner, Charles L. Mader and Manuel J. Urizar, Investigating Explosive and Material Properties by Use of the Plate Dent Test , Los Alamos Scientific Laboratory report LA-8591-MS (1980). 

A number of methods that provide information about the structure of a solid surface, its composition, and the oxidation states present have come into use. The recent explosion of activity in scanning probe microscopy has resulted in investigation of a wide variety of surface structures under a range of conditions. In addition, spectroscopic interrogation of the solid-high-vacuum interface elucidates structure and other atomic processes. 

There is no satisfactory chemical way of distinguishing betn een ethane and methane, both of which burn with an almost non-luminous flame this fact however is quite unimportant at this stage of the investigation. Hydrogen also burns with a non-luminous flame and w hen the open end of a test-tube full of the gas is placed in a Bunsen flame, a mild explosion with a very characteristic report takes place. 

M. Jacobson, A. R. Cooper, andj. Nagy, Explosivity of Metal Powders, U.S. Bureau of Miaes, Report of Investigations 6516, Washiagton, D.C., 1964. 

Fibers have been used by humans for thousands of years, but only in the twentieth century has there been such an explosion in fiber types available to the textile manufacturer. The advent of synthetic fibers possessing improved resiliency and dimensional stability has placed natural fibers, particularly cotton (qv), at an ostensible disadvantage. Before synthetics, various means to control the shrinkage, dimensional stability, and smooth-dry performance of cotton had been investigated, but the appearance of synthetics such as polyester has placed a greater sense of urgency on cotton interests to focus on the perceived deficiencies of natural fibers. 

Thermal Decomposition of GIO2. Chloiine dioxide decomposition in the gas phase is chaiacteiized by a slow induction period followed by a rapid autocatalytic phase that may be explosive if the initial concentration is above a partial pressure of 10.1 kPa (76 mm Hg) (27). Mechanistic investigations indicate that the intermediates formed include the unstable chlorine oxide, CI2O2. The presence of water vapor tends to extend the duration of the induction period, presumably by reaction with this intermediate. When water vapor concentration and temperature are both high, the decomposition of chlorine dioxide can proceed smoothly rather than explosively. Apparently under these conditions, all decomposition takes place in the induction period, and water vapor inhibits the autocatalytic phase altogether. The products of chlorine dioxide decomposition in the gas phase include chlorine, oxygen, HCl, HCIO, and HCIO. The ratios of products formed during decomposition depend on the concentration of water vapor and temperature (27). 

Finally, it must be pointed out that all devices suitable for use in explosion isolation—or, quite generally, all explosion protection devices used in practice—may be used only when their pressure rating, ignition breakthrough protection, and reliability have been proven in suitable investigations by competent bodies. 

An operator had tested dryer samples on a number of occasions. After the last sampling, he closed the manhole cover, put the dryer under vacuum, and started rotation of the dryer. A few minutes later an explosion and flash fire occurred, which self-extinguished. No one was injured. Investigations revealed that after... 

NFPA 921 Guide for Fire and Explosion Investigations. National Fire Protection Association, Quincy, MA. 

Have there been fires, explosions or chemical release incidents If yes, request the incident investigation data, including actions taken to prevent a reoccurrence. 

Investigate the potential for unconfmed vapor cloud explosions resulting from accidents at the flammable storage tank area. 

But probably the most serious barrier has been the paralysis that overtakes the inexperienced mind when it is faced with an explosion. This prevents many from recognizing an explosion as the orderly process it is. Like any orderly process, an explosive shock can be investigated, its effects recorded, understood, and used. The rapidity and violence of an explosion do not vitiate Newton s laws, nor those of thermodynamics, chemistry, or quantum mechanics. They do, however, force matter into new states quite different from those we customarily deal with. These provide stringent tests for some of our favorite assumptions about matter s bulk properties. 

Investigations in the field of shoek eompression of solid materials were originally performed for military purposes. Speeimens sueh as armor were subjected to either projectile impact or explosive detonation, and the severity and character of the resulting damage constituted the experimental data (see, e.g., Helie, 1840). Investigations of this type continue today, and although they certainly have their place, they are now considered more as engineering experiments than scientific research, inasmuch as they do little to illuminate the basic physics and material properties which determine the results of shock-compression events. 

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