When reservoir fluid levels decrease, air is drawn in through the reservoir breather. This also brings dirt and moisture! It costs much more to remove these contaminants than it does to keep them out!
Air Sentry® Breathers replace the standard breather cap or vent tube on a tank or reservoir. Air Sentry forces the air to pass through a 2 micron solid particulate filter and then through a bed of silica gel - the highest capacity absorbent available. After being dried, the air passes through a second 2 micron solid particle filter and enters the reservoir CLEAN AND DRY! They are easy to install using one of several adapters designed for different applications.