Air is composed of around 78% nitrogen and 21% oxygen with the remaining 1% other trace gases.
Unless your room is very small, like a cupboard, and you have a massive cylinder that releases enough nitrogen to displace all other gases, you still would have enough oxygen remaining in the room to sustain regular breathing. Moreover, as soon as the door to the room is opened, the gases within the room will quickly normalize to the standard composition of air.
On the other hand, if you employ Argon as your inert gas, you would need better ventilation as Argon is heavier than air and will pervade low to the ground. For example, this will be a concern if you had chosen the basement. Hope that helps.