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Instructions for Shipments Containing Biological Substance Category B, UN 3373

Diagnostic substances assigned to UN 3373 are regulated substances and must be packaged, marked and labeled appropriately. See below for appropriate steps to ensure your package's compliance.


Diagnostic substances assigned to UN 3373, are human or animal materials that are being transported only for the purpose of diagnosis or investigation. Such materials include excreta, blood and its components, as well as other tissues and fluids. Diagnostic substances do not include live infected animals. Although known as Diagnostic Substances, the proper shipping name of substances classified as UN3373 are “Biological Substance, Category B”.

If the source (the patient) is known to have a serious disease that can be readily transmitted and for which effective treatment and preventative measures are not usually available, then the substance must be assigned UN 2814 or UN 2900, as appropriate.


How to Prepare your shipment of Biological Substance, Category B using IATA packing instruction 650.

  1. Packaging
    1. Place your specimen in a leak proof, watertight primary receptacle. Use primary receptacles made of glass or plastic with a means to ensure a leakproof seal. A skirted stopper or metal crimp seal must be used. If you are using screw caps, they must be reinforced with adhesive tape. The primary receptacle must not contain more than 1 L for liquid specimens. For dried specimens, the primary receptacle must not exceed the outer packaging weight limit. The outer packaging weight limit can be obtained by either referring to the specs on the box or by contacting the manufacturer.

    2. Absorbent material is required for Biological Substance, Category B (UN 3373) shipments containing liquids. Place absorbent material between the primary and secondary receptacles, using enough material to absorb the entire contents of all primary receptacles.

    3. Use a secondary container that is leakproof for liquid specimens or sift proof for dried specimens. Choose only secondary containers certified by the manufacturer for Biological Substance, Category B (UN 3373) prior to use. Either your primary or secondary receptacle must be able to withstand, without leakage, an internal pressure differential of not less than 95 kPa in the range of -40ºC to 55ºC (-40ºF to 130ºF). To prevent contact between multiple fragile primary receptacles, individually wrap or separate them inside the secondary container.

    4. Use rigid outer packaging constructed of corrugated fiberboard, wood, metal, or plastic, or other equally strong material, including cylinders made of such materials and appropriately sized for the contents. Chipboard or paperboard boxes are unacceptable outer packaging. The completed packaging must be of good quality, strong enough to withstand the normal rigors of transportation without loss of contents as a result of vibration, changes in temperature, humidity, or pressure. Limit the total volume for liquid samples to 4 L and the total weight of dried samples to 4 kg per outer container. At least one surface of the outer packaging must have a minimum dimension of 100 mm x 100 mm (4" x 4"). Completed packages must be able to withstand a 4' (1.2-m) impact test. Before sealing the outer packaging, you must make an itemized list of the contents of the package and enclose the list between the secondary packaging and outer packaging.

  2. Marking and Labeling
    1. The name and address of both the shipper and recipient must be durably marked. The information provided on the shipping label is sufficient.
    2. The name and telephone number of a person responsible must be marked on the package.
    3. “Biological Substance, Category B” must appear in 6-mm-high text on the outer package adjacent to a diamond-shaped mark like the one shown here. The UN 3373 marking must be in the form of a square set at an angle of 45 degrees. Each side of the UN 3373 diamond should measure a minimum of 2" (50 mm).
  3. Specific Requirements for Refrigerated or frozen specimens: Ice, dry ice etc.
    1. When dry ice or liquid nitrogen is used to keep specimens cold, all applicable requirements of these regulations must be met. When used, ice or dry ice must be placed outside the secondary packaging or in the outer packaging or an overpack. Interior supports must be provided to secure the secondary packaging in the original position after the ice or dry ice has dissipated. If ice is used, the outside packaging or overpack must be leakproof. If dry ice is used, the packaging must be designed and constructed to permit the release of carbon dioxide gas to prevent a build-up of pressure that could rupture the packaging.
    2. The primary receptacle and the secondary packaging must maintain their integrity at the temperature of the refrigerant used as well as the temperatures and the pressures, which could result if refrigeration were to be lost.

More questions on shipping with Dry Ice? See our step-by-step guide here

Example of the triple packaging system for the packing and labeling of Category B, UN 3373 infectious substances.