Re: subducts
peach, that must be a small building.
IBC Section 714.2.1 requires individual protection for columns if they support more than two floor or a floor and a roof. If its three stories in height, individual protection is required and the shaft can't act as the protection.
So, to your question, assuming that its a small building, why not?
If the subducts are being used, its probably a residential building which is required to be sprinklered throughout. It's also required to have a fire alarm. Even if the sprinklers fail to control the fire, by the time the fire would get into the shaft and affect the column, people should be out of the building (and there are a whole lot of other problems since the sprinklers failed).