How can I add ventilation to my basement office?
Energy Recovery Ventilation (ERV)  You may want to consider either spot ERV or whole house ERV.

These devices both exhaust and intake fresh air, doing some energy exchange to reduce the impact on your air when the temperature differences between inside and outside are great.

Some ERV discussions here

As a spot unit, you could just run the unit in your office.  The Panasonic unit I've read about has automatic controls, but I would supplement them with a countdown timer to limit use even further as necessary. 

Leviton 12 Hour countdown timer





The divided wall cap means only 1 penetration is needed and it incorporates a pre filter for the incoming air.



Declaration:  No financial interest in Panasonic or Leviton.  I have used (personally) and installed (for customers) Panasonic fans and Leviton switches.