Special effects are used in movies to create a sense of excitement. They are most often seen in the action genre. Special effects are usually focused on creating an illusion on screen, but can also be physically happening as well.
Before the creation of CGI, many special effects were dangerous to shoot. Explosions were one of the most common forms in this regard. Experts in pyrotechnics were employed in Hollywood to make sure that these were done safely. Despite this it was still a dangerous aspect of production.
Vehicle crashes were also done using real life elements. These were usually too hazardous for the main stars to get involved in. Therefore lookalike stunt people were used to make it appear that the actor was in the action instead. These people are still used for perilous scenes in Hollywood today.
There have been a number of deaths and injuries due to physical special effects. An unknown amount of people drowned in the silent version of Ben Hur. Helicopter and motorcycle crashes have claimed the lives of stunt workers in more recent years. Because of this, CGI is used more predominantly.