An inflator which preferably has a gauge thereon and means for communicating with a medical connector or device. The inflator has a syringe body, a handle on the syringe body, a plunger which extends out from the handle and extends into the syringe body, and a plunger locking mechanism which is associated with the handle. The plunger locking mechanism includes an actuation lever which is configured to be depressed, thereby causing the plunger locking mechanism to actuate. The plunger locking mechanism includes a ratchet pawl which is configured to selectively engage corresponding ratchet structure, thereby locking the plunger in place, during which time the plunger is prevented from being retracted, but can still be advanced (i.e., pushed into the syringe body during pressurization). The plunger locking mechanism is configured such that when the actuation lever is released, the ratchet pawl disengages from the corresponding ratchet structure, thus freeing the plunger.
