Assessment of Explosion Hazards of Unstable Substances

Means are required to assess hazards by small-scale experiments. Those commonly used are based upon the science of conventional explosives with important modifications. Several types of explosion may occur: a detonation, propagating supersonically; a deflagration, propagating subsonically; so-called homogeneous explosion in which reaction occurs almost simultaneously throughout the mass. The event may be initiated by mechanical shock or by thermal stressing. If a substance can explode it is important to know how readily it can be initiated. Because the various modes of behaviour are not necessarily correlated it is necessary to carry out a variety of tests. Tests for detonability, deflagration, response to both ignition and external heating, and sensitivity are described. The interpretation of test results presents certain difficulties because of complex and sometimes imperfectly understood scaling laws. Some fundamental principles of explosion theory are invoked to aid extrapolation to large-scale situations and assessment of potential damage.