A tube segment sampler system (10) for withdrawing a fluid sample from a tube segment (100), the sampler (10) having a first tube piercing member (28) for piercing the tube segment at a first location and a second tube piercing member (28) for piercing the tube segment at a second location so as to allow air to be drawn into the tube segment (100) through one of the openings made by one of the piercing members (28) while fluid is withdrawn through the other of the openings.