Defective fireworks more common that you know
The butcher's bill from 2007 from fireworks mishaps is sobering; 7 deaths, 9,800 injuries. 5,000 of these were treated in emergency rooms during the Fourth of July holidays alone. 62% of the victims were male, 58% under 20. Hand injuries were the most common (1,400 injuries), followed by eyes and legs. Firecrackers were the primary culprit, with 900 injuries, followed by sparklers and bottle rockets.
In its survey, the CPSC heard many victims complain that their fireworks malfunctioned, so the commission launched an investigation of imported pyrotechnics (97% of imported fireworks come from China). With the help of the Bureau of Customs and Border Protection, it tested 211 shipments of fireworks, and found a staggering 49% contained fireworks which failed to meet U.S. safety standards.
Fireworks are a risky enough enterprise when they are made properly. Defective ones are a risk no-one should grasp. Until there is a way to determine the quality of the pyrotechnics in hand, I'd keep my fingers off them and safely in my pockets.