ISO Standards and the High Security Seals

The terms „ISO“, „ISO Standard“ or „ISO certified“ are extremely common in the everyday life of a company. All the companies in every industry are affected, also the manufacturers of security seals and the security seals themselves.

Which is the meaning of ISO?

ISO stands for International Organization for Standardization, an independent and international organisation with a membership of 164 national standards bodies. In such a complex world with so many different industries, companies, processes and products it can be very difficult to take a decision if the decision maker has not all the instruments to judge, for example, the quality of a product. At this regard comes into play ISO with its standards.

What is a standard?

A standard defines specifications of quality, safety, efficiency, reliability of a service, system, product or company. In the global world the importance of the standards is revealed also in the international trade as makes sure that certain conditions are unavoidably met and apply in every country. When a product is ISO certified the buyer has the guarantee that the product responds to defined specifications.

The standardisation speeds up the processes and makes a company more competitive as its services and products are accepted globally. The ISO certifications are always updated with new and state of the art specifications which follow the new technologies and procedures and have an expiry date: after few years the company has to be proofed again in order to extend the certification and get the ISO seal. The need to extend the certifications pushes the companies to improve its processes, systems and products, increasing for example the efficiency, quality and safety.

ISO certifications in the high security seals’ world: ISO 17712

Originally the norm was concerning just the shipping procedures related to transport via maritime freights towards the USA. After the 11th September 2001 the controls have been tightened to ensure security against terrorism, smuggling and theft. The regulations for shipping products via freight containers have become stricter so that the high security seals are nowadays used also for other kind of shipments.

The norm ISO 17712 uniforms the procedures for the classification, acceptance and withdrawal of mechanical freight container seals. The documents of this standard classify the seals (clause 5) and define the tests that a security seal must undergo to ensure that it cannot be tampered (clause 6). In addition, there is a list of criteria that the manufacturer of the security seal must meet (Annex A).

What is a high security seal?

As defined by the norm ISO 17712, a high security seal is constructed and manufactured of material such as metal or metal cable with the intent of delay intrusion. Based on the seals’ classification, a high security seal (H) generally must be removed with quality bolt cutters or cable cutters.
The high security seals are marked with “H” on the seals body.

The most common high security seals are bolt seals, as our Unisto Hi Genius, or cable seals, as our Unisto Metalo 40. Typical applications of high security seals are freight containers, trucks, trailers and all types of cargos and shipping containers.

Why are the high security seals marked with “H” and the indicative seals are not marked with “I”?

The indicative seals can be broken by hand and do not need to be subjected to the strength tests defined in the clauses. This is the reason why they are not marked with an “I”.

Tampering tests according to ISO 17712: which tests and which laboratories are accredited for the tests

There are different mechanical tests that a security seal must undertake to be classified as a high security seal (H):

a) Impact test: determines the resistance to an impact load at 18 °C and -27 °C.

b) Tensile test: determines the strength of a seal's locking mechanism.

c) Bending test: determines the resistance of a seal to failure under bending loads.

d) Shear test: tests the ability of a seal to withstand cutting with shearing blades, as might be implemented with bolt cutters.

In order to comply with ISO 17712, the testing laboratories must be certified according to ISO/IEC 17025 and be accredited for the four tests: impact, tensile, bending, shear. Only two laboratories can execute the tests: Mirdc and Dayton T. Brown. If you buy a high security seal from a supplier and the certification has not been issued by one of the two mentioned labs, then you are not buying a high security seal!

In accordance with ISO 17712, section 6, suitable tamper tests are set out in writing, executed and the test results documented. The aim of these manipulation tests is to ensure that the H seal cannot be opened and closed again without leaving visible traces of tampering.

ISO 17712 Annex A - «Seal manufacturers' security related practises»

Unisto stands since 1926 for highly tamper-proofed sealing solutions. It is increasingly clear that Security-Related Practices are as important as the physical strength of a seal. In order to demonstrate conformance to this annex, security seals manufacturers shall have a timely audit completed by an independent process certification provider specifically accredited to audit conformance with ISO 17712:2013. Unisto is also ISO 17712 Annex A conform.


To be defined as high security seal (H seal), a seal must be ISO 17712 inclusive Clause 6 certified.

Visual characteristics of a high security seal:

- a high security seal is made with robust material, as metal

- is marked with a “H” on the seal body

- it can be removed from a container only by using bolt cutters or cable cutters

Moreover a security seals manufacturer must be compliant to the Annex A “seal manufacturers’ security related practices”.


Unisto has also the following ISO certifications:

ISO 9001:2015 Quality Management System

ISO 14001:2015 Environmental Management System

ISO 45001:2018 Occupational Health and Safety Management System

Please find detailed information on the certifications’ page.