Migrating from OHSAS 18001 to ISO 45001
OHSAS 18001 was for many years the standard for occupational safety management. In 2018, ISO 45001 was published as its successor. The new standard is available from NEN and follows the High Level Structure . Since March 2021, OHSAS 18001 is no longer valid, and all certificates have expired or been transferred to ISO 45001.
If your organisation migrated at the time, or if you want to understand what changed compared with the old standard, this page gives an overview of the main differences.
The history
OHSAS 18001 (Occupational Health and Safety Assessment Series) was published in 1999 by a consortium of certification bodies, not by ISO. It was a widely accepted standard, but formally not an ISO standard.
In 2013, ISO started developing a true international standard for occupational safety. This resulted in ISO 45001, published in March 2018. Organisations were given three years to migrate. From 12 March 2021, all OHSAS 18001 certificates definitively lapsed.
In the Netherlands, several hundred organisations still held OHSAS 18001 certification in 2020. The majority migrated successfully to ISO 45001.
The main differences between OHSAS 18001 and ISO 45001
High Level Structure
The most fundamental difference is the structure. ISO 45001 follows the High Level Structure (HLS), the same structure as ISO 9001, ISO 14001 and other modern ISO management system standards.
OHSAS 18001 had its own structure, based on the old version of ISO 14001. With the move to ISO 45001, organisations can integrate their management systems much better.
| OHSAS 18001 | ISO 45001 |
|---|---|
| Own structure | High Level Structure |
| 4 chapters with requirements | 7 chapters with requirements (4-10) |
| Not integrable with ISO 9001:2015 | Fully integrable |
Context of the organisation
ISO 45001 introduces the concept of the “context of the organisation” (chapter 4). You must determine the internal and external factors that are relevant to your G&VW (health and safety at work) management system, and identify the needs and expectations of interested parties.
OHSAS 18001 did not have this explicitly. The assumption was that you started directly with policy and planning, without first analysing the wider context.
Leadership
ISO 45001 places more emphasis on top management leadership (chapter 5). Top management must personally take responsibility for the effectiveness of the system, not only allocate resources and appoint a representative.
The term “management representative” from OHSAS 18001 has disappeared. Responsibility can be delegated, but top management remains ultimately accountable.
Worker participation
This is one of the biggest changes. ISO 45001 makes worker participation much more central than OHSAS 18001 did.
OHSAS 18001 asked for “participation and consultation” but was less specific about what this involved. ISO 45001 specifies exactly when workers must be consulted and when they must participate. The standard also explicitly requires you to remove barriers to participation.
Worker participation is the most distinctive requirement of ISO 45001 compared with its predecessor. Organisations that migrated often had to put the most work into this area.
Risk-based thinking
ISO 45001 introduces the concept of “risks and opportunities”, which is broader than in OHSAS 18001. Alongside the traditional hazard identification and risk assessment, the standard also requires you to identify risks and opportunities linked to the context and interested parties.
This means you look not only at hazards in the workplace, but also at strategic risks and opportunities for the management system as a whole.
Opportunities
OHSAS 18001 focused on hazards and risks: what could go wrong? ISO 45001 also asks you to identify opportunities: possibilities to improve G&VW performance.
This shifts the focus from purely defensive (preventing harm) to also proactive (pursuing improvement).
Outsourcing and contractors
ISO 45001 is more explicit about controlling outsourced processes and working with contractors (clause 8.1.4). You must determine which requirements you set and how you ensure compliance.
OHSAS 18001 had less detailed requirements here. For organisations that worked a lot with subcontractors or suppliers, this was a point of attention during migration.
Terminology
Some terms have changed:
| OHSAS 18001 | ISO 45001 |
|---|---|
| Occupational health and safety (OHS) | Health and safety at work (G&VW or OH&S) |
| Procedure | Documented information |
| Record | Documented information |
| Workplace | Workplace (defined more broadly) |
| Hazard identification | Hazard identification (more extensive) |
Documentation requirements
ISO 45001 uses the term “documented information” instead of separate terms for documents, procedures and records. This gives more flexibility in how you record things.
The standard is less prescriptive about which procedures you must have. You must have “documented information” where the standard requires it, but the form is free.
The impact of the migration
Organisations that migrated from OHSAS 18001 to ISO 45001 typically made the following changes:
Context analysis added: A new element that did not exist in OHSAS. Internal and external factors and interested parties were identified.
Worker participation strengthened: Often the largest work package. Mechanisms to actively involve workers in risk identification, deciding on measures and incident investigation.
Documentation adjusted: The structure now follows the HLS. Terminology was updated. This was often the moment to streamline documentation.
Top management involvement increased: Top management was addressed more explicitly on their responsibility. Management reviews were adjusted.
Integration improved: Many organisations used the migration to better integrate their management systems with ISO 9001 and ISO 14001.
Lessons from the migration
Now that the migration is years behind us, there are lessons for organisations starting new with ISO 45001.
Take worker participation seriously: This was the stumbling block for many migrations. Take it seriously from the start, not as a checkbox but as an essential part of your system.
Do not underestimate context: The context analysis is not a paper exercise. A good analysis gives direction to your whole system.
Use integration: If you also have or want ISO 9001 or ISO 14001, design for integration from the start. This prevents merging later.
Involve top management: Without genuine commitment from the top, the system becomes a paper tiger. Invest in management commitment.
Still relevant?
The migration from OHSAS 18001 to ISO 45001 is complete. OHSAS 18001 no longer exists as a valid certification. So why is this information still relevant?
For organisations starting new with ISO 45001, it is useful to understand where the standard comes from. Some consultants and auditors still refer to OHSAS as a reference framework. Literature and templates based on OHSAS still circulate.
It also helps to understand what sets ISO 45001 apart. The emphasis on worker participation, the context analysis and risk-based thinking were deliberate choices in developing the standard, as improvements on what came before.
Next step
Ready to start with ISO 45001? Read the step-by-step plan or learn more about the requirements of the standard.