How long should a fire curtain be capable of holding back fire glow?

A fire curtain is designed as a passive fire protection measure to contain smoke and flames in a theater or performance space. The correct duration for which a fire curtain must be capable of holding back fire glow is 20 minutes. This time frame is generally set to provide a safe evacuation window for occupants and to limit the spread of fire to adjacent areas.

This 20-minute standard aligns with various building safety codes and regulations, which require sufficient time for emergency response and to protect lives. The intent is to allow time for emergency services to respond and for individuals to evacuate safely from the building.

Longer durations, such as 30 minutes, may not align with standard requirements for fire curtains, hence would be excessive, leading to unnecessary costs and potentially complicating the design or installation processes. More extended durations such as 10 or 15 minutes also fail to meet the commonly accepted standards for fire safety in theaters, making 20 minutes the appropriate and correct answer.