Explosives

Explosives are chemical substances or mixtures that release large amounts of energy rapidly, producing heat, gases, and a high‑pressure shock wave. They are designed to detonate or burn so quickly that a shock front forms and travels through the material. Detonation is a supersonic process that generates a powerful impulse; deflagration is a slower, subsonic burn. Explosives differ from propellants, which are intended to burn steadily to produce protracted pressure.

Common classifications distinguish sensitivity and use. Primary explosives are highly sensitive and used as initiators; secondary explosives are less sensitive and serve as the main charge; booster formulations increase detonation efficiency. Well-known examples include TNT (trinitrotoluene), RDX (cyclonite), HMX, PETN, and nitroglycerin. Black powder is an historical low explosive, while ammonium nitrate–fuel oil (ANFO) is widely used in mining and construction. Detonation velocity and brisance vary among materials and influence performance.

Applications span mining and quarrying, construction demolition, military ordnance, and pyrotechnics. Safety and regulation cover proper handling, storage, transport, and licensing, due to risks of accidental initiation, toxic fumes, and environmental harm. Responsible use emphasizes containment, quantity limits, and verification of stability and compatibility with other materials.

Historically, gunpowder originated in China, followed by development of nitroglycerin in the 19th century and Nobel's dynamite, which stabilized nitroglycerin with an absorbent. In the 20th century, more stable and specialized formulations emerged, along with stricter international controls on production, transport, and sale of energetic materials.