An alternative to the bulkier Starfleet environmental suits, life-support belts contained force field generators that maintained a standard Class-M (oxygen-nitrogen atmosphere) environment around the wearer. The belts also maintained temperatures and pressures suitable for humans and other humanoids.
Life-support belts were used by the crew of the U.S.S. Enterprise briefly in 2269, the year they were introduced, in the exploration of an ancient derelict ship on stardate 5221.3, on the oceanic planet Argo on stardate 5499.9, in the Beta Lyrae system on stardate 4187.3, and on a remote, airless asteroid near Orion space on stardate 6334.1. Force-field generation devices analogous to Starfleet life-support belts were also used by Kzinti pirates in 2269. Starfleet had phased out its use of life-support belts by 2271, in favor of an upgraded version of the traditional environmental suit.