Air Sentry X-Series Breathers are the perfect solution for high humidity and high dust environments. To extend the desiccant's life, the X-Series incorporates 2 check valves and a reusable top cap. The check valves provide a closed system until airflow is required, extending the service life of the desiccant. Specifically, the intake check valve allows airflow into the breather only when differential pressure between the atmosphere and fluid reservoir exceeds a 0.1 psi threshold, while the exhaust check valve permits air to exit the reservoir when the differential pressure exceeds a 2.0 psi threshold. A 0.1 psi check valve is also available for exhaust. When the gold silica gel has turned dark green, remove the reusable top cap from the bottom desiccant cartridge, dispose of the spent dark green desiccant cartridge, then use the same top cap with a replacement cartridge.