21. A package to be used for the transport of radioactive material or nuclear material substance by air shall comply with the following additional requirements:
(a) The temperature of the accessible surface of the package shall not exceed 50C at an ambient temperature of 38C with no account taken for insulation;
(b) The integrity of the containment system of the package shall not be impaired if they were exposed to ambient temperatures ranging from -40C to +55C; and
(c) If the package is designed to be used for the transport of radioactive material or nuclear material, the containment system of the package shall be so designed as to withstand, without leakage, an internal pressure which produces a pressure differential of not less than maximum normal operating pressure plus 95 kilopascals (kPa).