Abstract: A small micron filter unit comprising a main body connector unit, a single structure filter element, and an adapter unit for complementary engagement with the connector and for receiving and holding the single filter element. Preferably, the adapter unit is of soft material, such as flexible PVC, which allows the adapter unit to expand and receive a ring with ridge of the single filter element within a recess thereof. The ridge on the external circumference of the filter element ring forms a resilient indent in the flexible PVC material of the adapter. The compressive force exerted by the adapter around the filter ring functions to securely retain it in place and also forms a fluid and air axial seal. After assembly of the adapter unit within the connector body unit, an overall leakproof component filter device is formed.

Abstract: Negative pressure to accelerate flashback is formed by selective deformation of an elastomeric bladder. The bladder and a next adjacent cam means are enclosed in a housing, penetrated by a slide or roller engaging the cam surface. As the slide or roller moves along the cam surface, the bladder is selectively deformed first to close, then to evacuate distally and then to reopen at a negative differential pressure.

Abstract: A pair of compressible, hinged opposing arms enclose a bladder chamber, which in turn is coupled to the catheter. As the arms are compressed together, successive pivot fulcra close, in turn first pinching and closing, and then opening the bladder to create negative differential pressure against the catheter, and promoting flashback.