What is the maximum area of exterior wall openings for an unprotected building that has a fire separation system of 15 to less than 20 ft?

In the context of fire safety and building codes, the percentage of allowable exterior wall openings for an unprotected building is determined by the fire separation distance. When a building has a fire separation distance of 15 to less than 20 feet, building codes typically permit an opening area based on the risk associated with potential fire spread.

The correct choice indicates that the maximum opening area for unprotected buildings in this range is set at 25%. This percentage is derived from fire safety regulations that aim to limit the potential for fire exposure and spread between buildings. The rationale is to impose restrictions on larger openings which may contribute to increased risk.

This specific limit reflects the balance between allowing natural light and ventilation through exterior openings and preventing potential fire hazards. A lower percentage, such as 15% or less, would further reduce the risk, but as the fire separation distance increases, a slightly larger percentage can be deemed acceptable, leading to the 25% limit for distances between 15 and 20 feet.

Thus, adherence to this percentage ensures compliance with fire safety standards, ultimately protecting occupants and property from the dangers posed by fire events.