What does passing through two doors to enter a stairwell indicate?

Passing through two doors to enter a stairwell indicates that the stairs are isolated or wing stairs. This design serves to enhance building safety by creating a barrier against smoke and fire, which is critical in emergency situations. Isolated stairs are typically located in separate enclosures to ensure that they remain free of smoke and fire, allowing individuals to evacuate safely or for firefighters to ascend without encountering hazardous conditions. The two-door system is a key feature that emphasizes the intention behind these stairs: to provide a safe passage in case of emergencies.

Standard stairs and other types, such as non-training or emergency-use only, wouldn't typically require such protective measures. The isolation is a crucial safety feature that is especially important in high-rise buildings where smoke can quickly fill common areas, making access to safe exit routes a priority for building design and life safety protocols.