Containment Aseptic Isolator (CACI) providing a negative pressure environment for the preparation of sterile hazardous medications, composed of stainless steel and a polycarbonate front window with gloves. It is subdivided into an exchange chamber that is maintained at a higher negative pressure than the adjacent working chamber, which in turn has a negative pressure to the room, preventing contamination of the interior and the escape of material from it. The sliding door and work tray allow items to pass through the isolator prior to medication preparation, while the hinged front window facilitates maintenance and cleaning of the equipment. In order to guarantee the safety of health personnel, an alert system is included that identifies when the pressure of the equipment has deviated from its acceptable parameters.