Assessment of the permeability properties of cryopreservation outer bags used in NHSBT

This study was carried out to investigate leakage/transport across the bag material of six outer cryopreservation bags in common use within NHS Blood and Transplant. In order to do this two different leak testing procedures; coloured dye and hydrogen tracer gas, were used. The data obtained show that a coloured dye cannot permeate through the materials both at room temperature and following storage at liquid nitrogen temperature (? 196 °C). In addition, when filled with the smallest elemental molecule, hydrogen, in the form of a tracer gas, all of the bags only allowed trace amounts of hydrogen to escape, either through the seal or the bag material. The data indicated that each of the bag materials tested would be capable of preventing bacterial or viral cross-contamination as long as the material remained intact.