Federal Aviation Regulation Part 139 includes the certification of airports in the United States. This includes the training and certification of airport security personnel. When ticketed passengers pass through checkpoints they must declare certain items. Also, this is a time when certain items must be surrendered before passing on to a plane. In many cases a person carrying a restricted item is detained while airport security personal investigates the restricted item and the individual per airline safety regulations. Federal aviation regulations were introduced for the general safety of air crew, passengers, and the public at large. Some banned items may seem to be irrelevant but the regulations have been compiled to keep passengers from not only using items they bring on board but also combining items that accomplices bring on the same flight. This is especially true when it comes to chemicals. Many chemicals have hazardous reactions when mixed that can result in severe burns, blindness, and death. For this reason certain chemicals like bleach are completely banned and gels or liquids are allowed in containers larger than 3 ounces.