What does a pressure relief valve limit in a boiler system?

A pressure relief valve is a crucial safety component in boiler systems designed to prevent excessive pressure buildup. When the pressure within the boiler exceeds a predetermined safe limit, the relief valve automatically opens to release steam or water, thereby reducing the pressure to safe operating levels. This protects the boiler from potential damage or catastrophic failure due to overpressure conditions.

The other options do not accurately describe the primary function of a pressure relief valve. It does not directly control water temperature, nor does it have a role in limiting air pollution or enhancing fuel efficiency. Instead, its primary purpose is to maintain safe pressure levels within the system, ensuring safe operation and preventing hazardous situations related to pressure extremes.