When should firefighters use the purge valve on SCBA?

Using the purge valve on a self-contained breathing apparatus (SCBA) is primarily done to address situations where there is a malfunction in air delivery to the mask, specifically when the SCBA cylinder still contains air, but the wearer is not receiving it. This typically occurs when there is an issue with the regulator or the air supply line, resulting in a lack of airflow. By using the purge valve, firefighters can manually release air into the mask, allowing them to continue breathing safely until they can resolve the issue or exit the hazardous environment.

This action is critical for maintaining respiratory safety, as it provides a temporary solution that allows firefighters to remain operational in emergencies where air supply is compromised. It's essential for firefighters to know how to use the purge valve effectively to ensure their safety and the safety of their team during firefighting operations.