Level 3 biohazard was a containment field used on Federation starships for unstable lifeforms or objects.

In 2372, the Caretaker's remains began trembling slightly in the USS Voyager's sickbay, despite the fact he had been deceased for ten months. Lieutenant Tuvok suggested to Captain Kathryn Janeway that they place the remains in a level 3 biohazard field, as the Nacene had extraordinary abilities and Tuvok was concerned about what might happen next with the remains. It was later discovered that the Caretaker's remains were moving because of sporocystian life signs nearby where Voyager was heading. The sporocystian lifeform was later found to be Suspiria, the Caretaker's mate. (VOY: "Cold Fire")