What happens when you light firework rockets?

A fairground rocket is, in miniature, a solid-propellant engine — the same principle used by the strap-on boosters of a space launcher. The fuse starts the combustion of a black powder charge — potassium nitrate, charcoal and sulfur — packed into a cardboard tube with a nozzle. The gases escape through it at high speed and, through action and reaction, push the tube upward; the wooden stick stabilizes it the way fins would on a missile. At around 50-100 m of altitude, when the propellant runs out, an effect charge bursts and produces the bang, or scatters colored stars if it carries metal salts.

The bang of a firecracker or rocket easily exceeds 120 dB at a few meters, a level that can cause permanent hearing loss with a single exposure. Burns to hands and face are the most frequent injury, especially when the item is held after lighting or when handling one that failed to go off. Rockets, moreover, are the item that causes the most fires, because they fall while still burning dozens of meters from the launch point, onto roofs, dry vegetation or balconies.

In the European Union, pyrotechnic articles are classified into categories F1 to F4 according to their hazard level; rockets sold to the public are usually F2 or F3, with minimum ages of 16 and 18, and F4 can only be used by professionals. Local authorities can ban their use in specific areas or on specific dates, and near airfields there are additional restrictions because the lights and smoke can confuse pilots. Launching fireworks outside those limits carries fines and, if there is damage, civil or criminal liability.