A method for operating a biopsy apparatus includes providing a cannula having a lumen, a proximal portion, a closed distal end, and an orifice located on a circumferential surface of the cannula, the orifice being configured to receive a tissue sample into the lumen of the cannula providing a cutting sheath coaxially disposed with the cannula, the cutting sheath being configured to be movable relative to the cannula to selectively cover the orifice providing a pressure chamber coupled to the proximal portion of the cannula, the pressure chamber configured to contain a pressure providing a bifurcated valve assembly interposed between the cannula and the pressure chamber, the bifurcated valve assembly having a first valve and a second valve operating the first valve to release the pressure into the lumen of the cannula and operating the second valve to facilitate an inflow of air into the pressure chamber.
