An improved scent transfer device for collecting evidence at a crime scene. The device comprises a gas cartridge coupled to an air valve. A holder having a sterile pad positioned therein is secured to one end of a housing containing said air valve by locking protrusions. When gas from the cartridge is expelled into the air valve, a vacuum is created at the end of where the pad holder is attached when a switch is pressed, enabling a user to collect the scent on the pad. The pad can then be removed and stored in an evidence bag. An extension member which locks into the holder can be utilized to extend the capabilities of the device.