Colonoscopy is a very common diagnostic procedure and is considered relatively safe. Air insufflation is often used to increase the effectiveness of the procedure and decrease its duration. However, it is not uncommon for poor sphincter tone to cause loss of insufflation gas, thus complicating the workflow and lengthening the procedure. Air retention devices may address this shortcoming. In this paper we present an improved air retention device for colonoscopy and demonstrate its effectiveness through testing.