A primary life support system (PLSS), is a device connected to an astronaut or cosmonaut's spacesuit, which allows extra-vehicular activity with maximum freedom, independent of a spacecraft's life support system. A PLSS is generally worn like a backpack. The functions performed by the PLSS include:Regulating suit pressure Providing breathable oxygen Removing carbon dioxide, humidity, odors, and contaminants from breathing oxygen Cooling and recirculating oxygen through the pressure garment, and water through a Liquid Cooling and Ventilation Garment or Liquid Cooling Garment. Two-way voice communication Display or telemetry of suit health parameters Telemetry of an indicator of the wearer's immediate health

A liquid cooling garment (LCG) is a form-fitting garment that is used to remove body heat from the wearer in environments where evaporative cooling from sweating and open-air convection cooling does not work or is insufficient, or the wearer has a biological problem that hinders self-regulation of body temperature.