In the past, the International Building Code (IBC) has required pressurized stairwells to maintain pressurization with all exit doors closed. Most jurisdictions in the U.S. are adopting the 2015 IBC that can be interpreted as requiring exterior doors as opened or closed. In the early days of smoke control, it was thought that pressurized stairwells needed to be designed to (1) maintain pressurization with all stair doors closed, and (2) maintain pressurization with a specific number of stair doors opened. Recent research has changed this view. A 2016 ASHRAE research project (RP-1447) has shown that a tenable environment can be maintained in stairwells with many open doors provided that the stair door on the fire floor is closed. Small amounts of smoke that leak into the stairwell are quickly diluted resulting in a tenable environment in the stairwell. There are stairwell systems that are intended to maintain pressurization with a specific number of open doors, but many such systems are complex. One such system has dangerous failure modes. These issues are discussed including suggested stairwell pressurization systems.