Cap piercing station for closed container sampling system

A piercing station for piercing sample container caps or thick stoppers. The piercing station has a structural frame with two vertical guide rods. A carriage assembly is slidably mounted on the guide rods and is further driven to move up and down along the guide rods. The carriage assembly carries a blade holder, which in turn holds a piercing blade assembly. The blade assembly includes a center blade and two cross blades interlocked together, such that the blade assembly has a generally modified "H"-shaped cross section for piercing a cap on the sample container. Lubricant left in or on the sample container cap by the piercing station reduces the force required by the sample probe to penetrate thick stoppers for sample aspiration and level sensing. The "H"-shaped cut helps to equalize the pressure in the sample container during sampling, so that clot detection is more effective.