Fireworks safety sensitivity

Fireworks, when not properly handled, can result in injury, loss of life and property damage. The problems of safety are in many ways different from those of most explosives and propellants. In general, the sensitivity of fireworks to shock and impact is considerably less than that of many explosives and propellants. On the other hand, most fireworks are more sensitive to sparks and flame than most other explosive materials. 

Potassium chlorate becomes quite sensitive in contact with red phosphorus and ignites very easily by friction. These properties are used in match. When it is mixed with sulphur or compounds of sulphur like realgar, antimony trisulphide etc., the sensitivity to shock or friction is highly increased. According to the late professor S.Yamamoto of Tokyo University, when a mixture of potassium chlorate and realgar was shaped into a small tablet in a hand press and left on a table, a little while later the tablet caused spontaneous ignition and burnt out. He tried the same tests sevejjral times and the results were the same. He concluded that it was caused by inner friction which occurs with the recovery of the stress produced by the press(s. Yamamoto Studies in safety in firework manufacture 1(1959)3 ... 

B) includes noise compositions which are quite sensitive and snake compositions which exhibit curious phenomena, etc. It can be seen from the diagram that toy firework compositions, (A+B), are more numerous than those for ordinary fireworks (A). The reason is that, in the case of toy fireworks it is possible to increase the safety of the compositions to a high degree by complete division and isolation. Following this principle even some sensitive compositions which are never used for shells, exhibition fireworks etc. can be used for toy fireworks. For example, a composition which contains potassium chlorate and red phosphorus is used for pistol caps or another compositon which contains potassium chlorate and realgar is used for cracker balls. These compositions are generally used only for toy fireworks. 

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