Requirements for Type B M packages

Type B(M) packages shall meet the requirements for Type B(U) packages specified in para. 650, except that for packages to be transported solely within a specified country or solely between specified countries, conditions other than those given in paras 637,653-655 and 658-664 above may be assumed with the approval of the competent authorities of these countries. Notwithstanding, the requirements for Type B(U) packages specified in paras 653 and 658-664 shall be met as far as practicable. 

Intermittent venting of Type B(M) packages may be permitted during transport, provided that the operational controls for venting are acceptable to the relevant competent authorities. 

The intent is that the safety standards of Type B(M) packages, so designed and operated, provide a level of safety equivalent to that provided by Type B(U) packages. 

In order to provide safety equivalent to that which would be provided by a Type B(U) package, the design may include requirements that only gaseous materials should be allowed to be vented, that filters or alternative containment might be used, or that venting may only be performed under the direction of a qualified health physicist. 

Intermittent venting is permitted in order to allow a package to be relieved of a buildup of pressure which might, under normal conditions of transport (see paras 719-724) or when the package is subjected to the thermal test (see para. 728), cause it to fail to meet the Regulations. Radioactive release imder normal conditions and under accident conditions, where no operational controls are used, is limited, however, by the provisions of para. 656. 

Factors taken into account in such an assessment will include  

The location and orientation of the venting orifice in relation to the working position of the operator and the proximity of workers and members of the pnblic  

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The competent authority shall establish an approval certificate stating that the approved design meets the applicable requirements for Type B(M) packages and shall attribute to that design an identification mark. 

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