A force field is an energy barrier with many applications and varying degrees of strength. Although force fields had been in use for many years, the Star Fleet did not begin research on such a device until 2147. By the 24th century, Federation Star Fleet force fields were commonplace and were rated by intensity, ranging in strength from level 1-10. A level 10 force field is the strongest and would be used, for example, during a scientific experiment of which the outcome is unknown, or known to be explosive in nature.
The effects of a force field on its surroundings vary greatly. Contact with a force field may cause anything from a slight tingle to death. Most force fields are non-lethal, although some civilizations prefer the lethal variety. If a force field is active, an object or transporter beam generally cannot pass through it, although this is not always the case.
Force fields can be activated from various locations. On Star Fleet starships there are emitter points at almost every junction along every corridor. The computer can be programmed to run a series of force field activations and de-activations within the ship, effectively creating a protected corridor that can follow a person.