Legal fireworks give you enough time to get out of their way. SKatzenberger/iStock via Getty ImagesWhat makes fireworks legal or illegal? The Consumer Product Safety Commission (CPSC) instigated a \"fuse burn time\" standard that legal fireworks need to meet. Typically, consumer-grade fireworks must have a fuse burn time of between three and nine seconds so users can get away from the fireworks before they go off. Legal fireworks are also limited to containing 50 milligrams of pyrotechnic material.