Atmospheric system
The atmospheric system was a system aboard the  that regulated atmosphere aboard the starship. 

A panel labeled "atmospheric system" located near section 2 on deck 9 was being worked on by Barnhart moments before he was killed by the M-113 creature. ()

Another panel was in a corridor of the ship, near a set of quarters that, in 2266, were assigned to Charles Evans. Moments before a force field was activated in the door to Evans' quarters, the atmospheric system panel was momentarily tweaked by Harrison, though operating it wasn't one of his usual duties. ()

See also 
Air handling system
Atmospheric stabilization
Environmental control
Life support system
Life support technology