A catheter assembly system comprising: a catheter adapter having an inner lumen extending between a proximal opening of the catheter adapter and a distal end of the catheter adapter ; a septum disposed within and selectively sealing the inner lumen ; a vent channel that fluidly connects the proximal opening and distal end of the catheter adapter by bypassing the septum ; a septum activator disposed within the inner lumen proximal to the septum and having a proximal opening , the septum activator being configured to advance distally through a slit in the septum ; and an activator attachment comprising: a proximal end having a proximal opening ; a connector portion comprising a set of threads; a probe member ; and an extension member that extends from the distal end of the probe member , wherein a lumen of the activator attachment extends from the proximal opening of the activator attachment through the probe member and the extension member , characterized in that in response to the activator attachment being inserted into the proximal opening of the catheter adapter to a first position, the probe member inserts into the proximal opening of the catheter adapter and contacts a proximal end of the septum activator , the extension member inserts into the proximal opening of the septum activator , the lumen is in fluid communication with the inner lumen of the catheter adapter , and the slit in the septum is closed, and in response to the connector portion being threaded to the proximal end of the catheter adapter , the activator attachment is distally advanced from the first position to a second position, and the probe member forces the septum activator distally through the septum . a catheter adapter having an inner lumen extending between a proximal opening of the catheter adapter and a distal end of the catheter adapter ; a septum disposed within and selectively sealing the inner lumen ; a vent channel that fluidly connects the proximal opening and distal end of the catheter adapter by bypassing the septum ; a septum activator disposed within the inner lumen proximal to the septum and having a proximal opening , the septum activator being configured to advance distally through a slit in the septum ; and an activator attachment comprising: a proximal end having a proximal opening ; a connector portion comprising a set of threads; a probe member ; and an extension member that extends from the distal end of the probe member , wherein a lumen of the activator attachment extends from the proximal opening of the activator attachment through the probe member and the extension member , a proximal end having a proximal opening ; a connector portion comprising a set of threads; a probe member ; and an extension member that extends from the distal end of the probe member , wherein a lumen of the activator attachment extends from the proximal opening of the activator attachment through the probe member and the extension member , characterized in that in response to the activator attachment being inserted into the proximal opening of the catheter adapter to a first position, the probe member inserts into the proximal opening of the catheter adapter and contacts a proximal end of the septum activator , the extension member inserts into the proximal opening of the septum activator , the lumen is in fluid communication with the inner lumen of the catheter adapter , and the slit in the septum is closed, and in response to the connector portion being threaded to the proximal end of the catheter adapter , the activator attachment is distally advanced from the first position to a second position, and the probe member forces the septum activator distally through the septum . <EOS>