A septum is penetrable by a needle for decontamination by physical interaction. The septum can include a peripheral portion, an exterior surface, and an interior surface. A penetration portion extends between the exterior and interior surfaces, is spaced inwardly of the peripheral portion, and is penetrable by the needle or other penetrating element. A flex portion is located between the penetration portion and the peripheral portion. A thicker portion extends between the flex portion and the penetration portion, and defines an increased thickness between the exterior and interior surfaces relative to the flex portion. The flex portion is flexible inwardly relative to the peripheral portion during penetration of the penetration portion by a needle or other penetrating element. The penetration portion physically interacts with and decontaminates the needle when it penetrates the septum. The septum may also reduce or prevent retrograde contamination when the needle is withdrawn.