Abstract: A sleeve for preventing backflow and cross-contamination between patients of fluid and particulate matter as well as other contaminants present within a dental/medical suctioning device. The sleeve includes a sleeve inlet end that sealingly attaches to and surrounds at least a portion of the suctioning device the vacuum hose to the evacuator tip. The sleeve also has a sleeve exhaust end that is inserted into the control valve and can reside within the interior lumen of the vacuum hose during normal suction operation. During operation, the sleeve provides a seal between the patient contact part and the control valve of the suctioning device. The proximate end collapses, seals, and/or provides a barrier when the suctioning device does not draw a vacuum away from the patient and towards the vacuum source.