An autotransfusion system for collecting blood from a patient and reinfusing the blood back into the patient is disclosed. The system includes a collection unit, a manually operable portable suction evacuator removably connected to the collection unit, and a blood reinfusion bag removably connected to the collection unit. The collection unit includes a collection chamber that is oversized relative to the volume of blood that the unit is intended to contain, and an airflow port located and oriented in the collection chamber to prevent blood from leaking into the port when the collection unit is oriented upright or on its side. When connected to the patient, the collection unit and portable suction evacuator are maintained free of blood by enclosing them within a substantially transparent, flexible envelope. The envelope enables the unit and evacuator to be connected and set-up for proper operation while preventing blood from contacting the outer surfaces of the unit and evacuator.