Some substances are safe to ship only after a period of weathering following production, to allow chemical reaction or internal self-heating to stabilize. Certification should be provided by the shipper to confirm that a sufficient period of weathering has been allowed before shipment.

Requirement for a weathering certificate¹⁰¹ appears in the IMDG Code Dangerous Goods List under column 17 Properties and Observations. For example, UN 1376, IRON OXIDE, SPENT mentions that ‘this substance should have been cooled and weathered for not less than eight weeks before shipment, unless packed in a metal drum’.

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¹⁰¹IMDG Code, 2022 Edition Amendment 41-22, Section 5.4.4.1.1

Some substances included in the IMDG Code Dangerous Goods List are not hazardous under certain circumstances, and do not need to be treated as dangerous goods. Example: UN 1362, CARBON, ACTIVATED is listed as “spontaneously combustible”. However, production methods for activated carbon vary, and some production processes produce activated carbon that is not self-heating and therefore the product is not subject to the IMDG Code.

If the shipper claims that his product is not hazardous and should therefore be exempt¹⁰² from IMDG rules for any reason, a certificate from the competent authority of the country where the product is made explaining why his product should be exempted is likely to be requested by the shipping company. A copy of this certificate should be attached to the transport documents to travel with the load to avoid potential difficulties with inspection authorities and at transhipment ports.

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¹⁰² IMDG Code, 2022 Edition Amendment 41-22, Section 5.4.4.1.2

Letters of indemnity form no part of the IMDG Code, but shipping line policy may request the shipper to supply one as a condition of acceptance for controlled temperature dangerous goods. These generally state that while the line will carry out due diligence to care for the machinery in the cargo transport unit controlling the temperature, the line bears no responsibility for consequences of failure or malfunction of that machinery, or that the shipper bears full liability for any consequences arising from the nature of the substance carried.

There are occasional circumstances when shippers request a shipment to be made under conditions that are prohibited by the IMDG Code, but are nevertheless considered safe, because special compensatory measures have been taken. In such cases the shipper is entitled to request the competent authority of the country of shipment to judge the measures, and, if found satisfactory, to issue a certificate of approval for the shipment to go ahead. The competent authority¹⁰³ will consider the request and only if convinced that there is no increased risk to safety, will issue a certificate of approval. This must be sent to the shipping line and a copy must travel with the goods.

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¹⁰³ IMDG Code, 2022 Edition Amendment 41-22, Chapter 7.9.2

There are no provisions in the IMDG Code to provide packing certificates when dangerous goods are loaded into tank containers. The equivalent for tanks is a “filling certificate” issued when the tank is filled to state that the tank is compatible with the product and has been filled and closed correctly. There is no requirement in the IMDG Code for the shipper to provide a filling certificate.

However, many shipping lines request a copy of the tank inspection certificate. This is a certificate issued after a mandatory tank inspection carried out when tanks are first commissioned and at 2.5 yearly intervals thereafter to state that the tank is in good condition and meets the design specifications.