Depressor

A Depressor is an item used mainly by the Oscdean State military forces during high atmospheric or off planetary operations. The purpose of a depressor is to provide temporary O2 in tight spaces, as the canister undergoes a rapid chemical reaction to provide an hour and a half of oxygen for one man. The canister weights around 4.24 lb, and around 7 inches tall, small enough to be carried around with ease. 
In order to activate the Depressor, one must twist both ends of the canister and pull, igniting the chemical chain reaction.