My take on the underground gas/vent stuff.
Make a block that has the same texture as the stone, inserted into the layers underground. You strike the block while mining it activates an AoE buff that depletes your characters O2.
Replace the vent system and in turn have an "air scrubber unit" that needs power (this will also have an AoE to debuff the O2 depletion buff).
The "air scrubber unit" has components, that will deplete over 'X' amount of time that you need to replace (more scrubber units = more time in between that you need to replace).
Or if a vent system is a must: piggy back with the electrical mechanic and have a tool similar to wire tool,"Vent pipe tool". Has the same properties as the wire.
Connect underground duct fanA to the above ground duct fanB. Fan A or Fan B needs to be connected to a generator. The "pipe" from the Vent Pipe Tool also acts as a wire to power the whole thing.
Laying the pipe: >.> you need to collect plastic and wire.
Fan A uses an AoE buff to debuff (whatever) gas.
*I'm just looking at it from a possible mod perspective though.
Edit: With the vent pipe tool being like the electrical mechanic wire laying abilities, the system only needs to check that everything is connected periodically between all points much like having relays, generator and turrets do.