Vacsuit

A vacsuit, short for vacuum suit, was a variation on a standard specifically intended as a safety measure against  for crews of starships and space stations.

Technology
A vacsuit was skintight and flexible, allowing range of movement equal to a standard Starfleet uniform. The helmet was designed to seal automatically in the event of a catastrophic drop in ambient air pressure. It carried four hours of compressed air, although the built-in air scrubbers increased that to ten hours. It was painted brightly in divisional colors and featured a radio frequency transponder to help search-and-rescue teams locate ejected crew.

The suits were tough enough to provide some shrapnel protection and could stand up briefly to small arms fire. In the event of a suit puncture on an extremity, it was designed to clamp down into a tourniquet above the hole on the reasoning that it was better to lose a limb than the entire person.

Although each suit was custom-fitted for its wearer, this was done by taking a full-body scan and feeding the results into a computer algorithm to produce a pattern. During all Starfleet recruits were trained to don their suits in 90 seconds or less.

History
In 2391 Starfleet began issuing vacsuits to all crew members, who were to put them on when combat was expected. As expected, this substantially reduced battle casualties.

In 2409, when a squadron of Klingon Defense Force Birds-of-Prey were detected closing on Utopia Planitia Fleet Yards at high warp, shipyard commander Rear Admiral B'Elanna Torres ordered the yard to battle stations and to get the crew into vacsuits. When the Klingons arrived they inflicted severe damage on the facilities and on docked ships. Approximately 400 people, including Ensign Kaitlyn McMillan, were blown out into space or otherwise left in vacuum through various hull breaches, but 290 survived in their suits.

In December of that year Captain Kanril Eleya of the USS Bajor ordered her crew into vacsuits as the starship responded to a distress signal from.

Behind the scenes
The vacsuit was inspired by skinsuits in the  novel franchise.