When swinging type fire shutters are installed in exterior openings, how many rows must be arranged to be opened from the outside?

The correct number of vertical rows required to be arranged for swinging type fire shutters to be opened from the outside is three. This requirement is established to ensure a sufficient level of accessibility and operational efficiency in emergencies, allowing personnel or first responders to efficiently operate the shutters in case of a fire or hazardous situation.

Three vertical rows strike a balance between ease of access and structural considerations for the fire shutter. Having three rows can help facilitate operation without overwhelming the mechanism or creating potential for user error. Each row is designed to provide a secure yet accessible means to open the shutters, ensuring that they can be quickly and effectively managed when needed.

The other options regarding four, five, or six vertical rows exceed the necessary requirements for operational efficiency and practical design considerations, as more rows could complicate the mechanism without providing significant benefits in terms of accessibility.