A closed loop infusion system controls the rate that fluid is infused into the body of a user. Because condensation can build-up in a filter of the gas analyzer, it needs to be purged from the analyzer so that accurate readings can be made. The blade has a profile taken in a plane oriented substantially perpendicular to the longitudinal axis of the blade. A selector available to the driver signals the controller for selectively enabling use of the secondary brake system in conjunction with the primary brake system.