Stinky Shared Hallways and Stairwells

[Andrew Flora]

Hi, 

I have a large multi family property that I self manage.  It has 3 common indoor hallways that are about 120ft long 1 on each floor and stairwells.  In the past the building has allowed smoking, and I have since changed that but the hallways smell of smoke and of just a generally musty and stale air.

The tenants seem used to it but I would like to freshen the place up a bit, especially since I spent several hours a week there.  What is the best way to fix this issue?

There's not much ventilation so I thought about adding vent fans or windows to the hallways and stairwells as they all have at least 1 exterior wall.

A cheaper and easier solution I thought might be a commercial grade air purifier in each hallway and some plug in air fresheners.

Every room has 2 vent fans, a window, and a through the wall air conditioner so the rooms have good ventilation but the hallways can get stagnant, especially in the summer when it is hot(no a/c in the hallways and stairwells).

Any suggestions that don't cost a fortune? 

Thanks