The sign accompanying the PLSS. It reads
Portable Life Support System
To provide a suitable protective environment during both lunar surface and free
space excursions, the astronaut carried on his back a compact assembly of
various environmental control devices, which formed the portable life support
The PLSS supplied breathing oxygen; controlled suit pressure; recycled oxygen
by removing carbon dioxide, odors, moisture, and some trace contaminant gases;
controlled temperature; provided warnings of system malfunctions; and provided
voice communications and telemetry data.
The portable life support system supplied oxygen to the pressure garment
assembly and cooling water to the liquid cooling garment. The PLSS
subsystems were an oxygen ventilating circuit, a primary oxygen subsystem, a
liquid transport loop, a feedwater loop, and an electrical power subsystem.
A separate emergency system provided oxygen for breathing, suit pressure, and
cooling in case of PLSS failure. The system was called the oxygen purge system
(OPS) and was manually activated.