After a dry system has been in service for 3 years, what is required for an air test?

In the context of maintaining the integrity of a dry sprinkler system, a key requirement after a system has been in service for a specific duration, such as three years, is to ensure that the system remains leak-proof and that the pressure is sufficiently maintained.

The correct approach is to perform the air test at the system's working pressure for a designated period. This method ensures that the system is tested under conditions that are representative of its normal operational environment. By testing the system at the working pressure, you can accurately assess whether there are any leaks or weaknesses in the piping or fittings that could compromise the system's functionality.

This procedure is in line with industry standards and serves to ensure that any potential issues are identified before they can lead to system failures during a fire event. It’s crucial for the safety and reliability of the fire protection system.

The other options imply either a lower pressure or an extended time frame that does not align with the industry standards for maintaining operational readiness after the specified duration in service. Therefore, testing at system working pressure for an adequate duration is vital for compliance and performance assurance.