What is the primary function of a dry-pipe sprinkler system?

The primary function of a dry-pipe sprinkler system is to utilize air or nitrogen under pressure to keep the water in the pipes at bay until a fire occurs. In this system, the pipes are filled with pressurized air or gas, and there is water stored in a distant location, typically a tank or reservoir. When a fire triggers an individual sprinkler head, the pressurized air is released, allowing the water to flow into the piping system and discharge through the opened sprinkler head.

This design is particularly advantageous in environments subject to freezing temperatures because it prevents water from sitting in the pipes and freezing, which could cause pipe damage and system failures. The system can be installed in unheated buildings or areas where temperature maintenance is difficult. Hence, the correct answer showcases the unique mechanism of leveraging air or nitrogen pressure to facilitate water flow only when needed, which is a key characteristic of dry-pipe systems.