These are fully closed-circuit devices that recirculate all the gas you're breathing, taking out the carbon dioxide and replenishing the gas with oxygen.
(These; are; fully closed-circuit devices that recirculate all the gas) (fully closed-circuit devices; recirculate; all the gas you're breathing) (all the gas; 're breathing; you)
These fully closed-circuit devices all the gas
are recirculate 're breathing
fully closed-circuit devices that recirculate all the gas
all the gas you're breathing
you