OHSAS 18001: History and Withdrawal Timeline, from 1999 to ISO 45001
For two decades OHSAS 18001 was the world's most widely used occupational health and safety management system specification. Then it was withdrawn. This article tells the story in a short timeline: where OHSAS 18001 came from, why it was replaced and which dates mattered. If you still hold or quote an old OHSAS certificate, see our OHSAS 18001 migration page and our ISO 45001 service.
Edition status (checked October 2026): ISO 45001:2018 is the current published edition. ISO is revising it (ISO/DIS 45001 went to ballot in 2026, next edition planned for 2027), but the revision is not yet published.
Before OHSAS: the gap in international standards
By the early 1990s, the ISO 9000 family for quality was widely adopted, and in 1996 the ISO 14001 standard for environmental management was published. A parallel standard for occupational health and safety was widely discussed, but in the mid-1990s ISO decided not to develop one, as there was no consensus at the time. Organisations and certification bodies that wanted a recognised way to assess and certify OH&S management systems were left without an international standard.
1999: OHSAS 18001 is published
To fill the gap, a group of national standards bodies, certification bodies and specialist institutes developed the Occupational Health and Safety Assessment Series, known as OHSAS. The group published OHSAS 18001 in 1999 as a specification against which an OH&S management system could be assessed and certified, and OHSAS 18002 as guidance for implementation. OHSAS 18001 was designed to be compatible with ISO 9001 and ISO 14001. Although it was widely adopted, it was never an ISO standard, and it was published by the participating organisations rather than by ISO.
2007: the second edition
OHSAS 18001 was revised in 2007 to improve alignment with ISO 14001:2004 and to clarify points such as incident investigation and the role of health. OHSAS 18001:2007 remained the basis for most OH&S certificates worldwide for more than a decade. It focused mainly on hazard identification, risk assessment, operational control and legal compliance.
2013 to 2018: ISO takes up the work
In 2013 ISO established a project committee, ISO/PC 283, to develop an international OH&S management system standard. The committee brought together experts from many countries, along with liaison organisations such as the International Labour Organization. The project was designed from the start to use the same high-level structure as ISO 9001:2015 and ISO 14001:2015, which made integration easier. After several drafts and public comment, ISO 45001:2018 was published on 12 March 2018.
What changed with ISO 45001
- Context of the organisation: understanding internal and external issues and the needs of workers and other interested parties.
- Leadership and worker participation: top management is accountable, and workers must be consulted and involved.
- Risks and opportunities: OH&S risks and opportunities are planned, not only hazards.
- Hierarchy of controls and management of change: a specific requirement to prioritise controls, covered in our guide to the hierarchy of controls.
- Contractors and outsourcing: clear requirements to control them.
- High-level structure: the ten-clause layout shared with other ISO management system standards.
The withdrawal and migration timeline
| Date | Event |
|---|---|
| 1999 | OHSAS 18001 and OHSAS 18002 published |
| 2007 | OHSAS 18001:2007 published |
| 2013 | ISO/PC 283 starts developing the international standard |
| 12 March 2018 | ISO 45001:2018 published; start of a three-year migration period for OHSAS 18001 certificates |
| 12 March 2021 | Original end of the migration period; OHSAS 18001 withdrawn |
| 30 September 2021 | End of the migration period for accredited certification after the International Accreditation Forum granted a six-month extension because of COVID-19 |
After the final deadline, OHSAS 18001 certificates were no longer valid for accredited certification, and organisations that wanted to keep an accredited OH&S certificate needed one against ISO 45001.
Why the change mattered to organisations
For many companies, migration was an opportunity to move from a paper-based hazard register towards leadership-driven safety management. For others it was a rushed compliance exercise. Those who treated it as a people project, with training, communication and worker involvement, usually found it easier. We discuss that approach in our article on leading ISO transitions with people at the centre.
Is anything of OHSAS 18001 still useful?
Yes. Hazard registers, procedures, legal registers, training records, incident logs and audit reports built under OHSAS 18001 are valuable starting material for an ISO 45001 system. The task is to review them against the new requirements, fill gaps, and demonstrate that the system operates. When you are ready for an external audit, our guide on preparing for Stage 1 and Stage 2 audits explains what to expect.
What the history teaches
The OHSAS story shows how voluntary, industry-led specifications can set the benchmark until an international consensus emerges, and how quickly a market can move once an ISO standard exists. It also shows the value of keeping management systems flexible: organisations that kept their safety documentation simple, process-based and owned by line managers adapted fastest. Those that had built heavy, auditor-oriented paperwork needed the most rework. Whatever the next revision is, the lesson is the same: build for the way people really work, and keep evidence of how risks are controlled.
Key takeaways
- OHSAS 18001 filled a gap between 1999 and 2018 but was never an ISO standard.
- ISO 45001:2018 replaced it, and the migration period ended on 30 September 2021.
- Existing OHSAS documentation is a good basis for ISO 45001, but leadership and worker participation require real change in how safety is managed.
Frequently Asked Questions
When was OHSAS 18001 first published?
In 1999, with a second edition in 2007.
Who developed OHSAS 18001?
A group of national standards bodies, certification bodies and specialist institutes, rather than ISO itself.
When was ISO 45001 published?
On 12 March 2018.
When did OHSAS 18001 certificates stop being valid?
The migration period ended on 30 September 2021 after a six-month extension due to COVID-19. After that date, OHSAS 18001 certificates were no longer valid for accredited certification.
What happened to OHSAS 18002?
It was the guidance document for OHSAS 18001 and was withdrawn along with it. ISO 45002 now provides guidelines for implementing ISO 45001.
Related Articles
- Hierarchy of Controls Explained: Better Workplace Risk Assessment with Real Examples
- Leading ISO transitions with people at the centre
- How to Prepare for an ISO Audit: What Happens in Stage 1 and Stage 2
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