If sample must be shipped to the laboratory, follow procedures above and pack frozen sample in contact with dry ice to maintain temperature as low as possible during shipment. Pack sample in a container such as a paint can or Nalgene bottles which are impervious to CO gas, because absorption of CO2 by the sample could lower the pH and diminish the viability of C. perfringens. Store sample at -70 to -90°F on receipt and keep at this temperature until examined, preferably within a few days