The air you’re pushing out needs to be replaced somehow. If there’s only one window open, then the only place for air to come in is through that same window, and it won’t work too well. But, if you have two windows open on opposite sides of the room, then that would work very well. If there is a second window open anywhere in the house, the air will be pulled through the house from that window.
But, also simply stirring it around will dilute it, and make it less noticeable.
Any room that was so airtight this would be a concern has already taken that into account. Air will get in under the door, through cracks or fixtures, or even the window the fan is in.
The air you’re pushing out needs to be replaced somehow. If there’s only one window open, then the only place for air to come in is through that same window, and it won’t work too well. But, if you have two windows open on opposite sides of the room, then that would work very well. If there is a second window open anywhere in the house, the air will be pulled through the house from that window.
But, also simply stirring it around will dilute it, and make it less noticeable.
Any room that was so airtight this would be a concern has already taken that into account. Air will get in under the door, through cracks or fixtures, or even the window the fan is in.