It's advised that you get the level 4 air filter upgrade from the medical wing as soon as possible, because it will allow you access to the DZ's entire subway system, which can prove invaluable when attempting to both escape and get the drop on other players. First and foremost, if you go rogue, heading down into the subway with a level 4 filter may prevent some of your pursuers from following you due to not having the filter, and secondly, you can use the hordes of NPCs down there as a distraction: if you can run past them, they will begin shooting at your pursuers as they pass through and possibly keep them pre-occupied. With its twisting, boxed-in tunnels, it also massively lessens the likelihood of getting sneak attacked as you would out in the open. If you ever get into a spot of trouble, don't underestimate the subway as an option for respite.