Life Support Systems
Intro
Exact implementation of life support systems among ships will vary according to ship design and ship engineering (the actual engineering and design of a ship) as well as by factions and species and even commercial ship builders.
Ducts
The ducting system of any ship or station is likely to be intricate and could be compared to the blood vessels and capillaries of a human body. It would be important to note, that despite such the intricate nature of atmosphere delivering life support, this system would be most effective as a distributive which also provides redundancy. Ducting for this system would likely not be large enough that it would provide a means of traveling through the ship, especially if it effectively bypassed all the security and tracking measures on a ship.
USI ships specifically would not have ducts that would allow this to happen. And its *very* sci-fi cliche'.
Fire Suppression
Fire suppression is important on a ship in order to prevent a ship from literally internally allowing itself to become consumed in the event. Fire Suppression is accomplished on many ships, specifically USI Ships, by the use of an inert heavy gas, which is non-lethal and non-flammable. The gas can be simply used to quickly fill in a room or even blown onto a fire to immediately deprive it of oxygen rendering it dead. This has many advantages as it provides no cleanup, and can be as quickly vented out as it was in allowing for it to be used in situations where a fire is in a location where a life form may be present.