ILO Convention No. 155: International Principles for Occupational Health and Safety

Adopted in 1981, the International Labour Organization’s Convention No. 155 establishes principles for developing a national occupational health and safety policy. Recognized as a fundamental ILO Convention in 2022, it is a major international reference for preventing occupational accidents and diseases.

Introduction

The International Labour Organization (ILO), a specialized agency of the United Nations dealing with the world of work, has developed more than 40 international instruments specifically addressing occupational safety and health, alongside many other instruments covering related issues.

Adopted on 22 June 1981, Convention No. 155 concerning Occupational Safety and Health and the Working Environment establishes principles for a national policy on occupational risk prevention. It also sets out responsibilities for public authorities, employers and workers.

Since June 2022, this Convention has been recognized as a fundamental ILO Convention, alongside Convention No. 187 concerning the Promotional Framework for Occupational Safety and Health.

These two instruments should be distinguished. Convention No. 155 primarily addresses national policy and preventive measures, whereas Convention No. 187 focuses on establishing a national framework for the continuous improvement of occupational safety and health.

1. Fundamental Principles of Convention No. 155

Convention No. 155 calls on ratifying States to formulate, implement and periodically review a coherent national occupational safety and health policy, in consultation with representative employers’ and workers’ organizations.

Under Articles 4 and 5, this policy aims to prevent occupational accidents and work-related harm by reducing the causes of hazards in the working environment.

Its scope includes:

• The design, layout and maintenance of workplaces.
• The safety of machinery, equipment and tools.
• The identification and control of chemical, physical and biological hazards.
• Work organization and preventive methods.
• Worker training and information.
• Cooperation between public authorities, employers and workers.

The overall objective is to prevent risks at their source, as far as reasonably practicable, rather than relying solely on measures taken after an accident has occurred.

2. Employers’ Responsibilities

Convention No. 155, particularly Articles 16 to 19, sets out provisions concerning measures to be implemented at enterprise level in States bound by the Convention.

Its principles also provide an international reference for organizations seeking to improve their occupational risk prevention systems.

Key measures include:

1. Comply with applicable legislation: Identify and implement the legal and regulatory requirements governing occupational health and safety.
2. Assess occupational risks: Identify hazards associated with facilities, equipment, substances and work organization.
3. Implement preventive measures: Eliminate hazards where possible and reduce risks to an acceptable level.
4. Provide appropriate protective equipment: Supply equipment suited to identified risks and ensure its proper use.
5. Train and inform workers: Explain workplace hazards, safety instructions and emergency procedures.
6. Consult workers: Encourage their participation in hazard identification and the improvement of working conditions.
7. Prepare for emergencies: Organize first aid and establish procedures for accidents and dangerous situations.

Prevention should be integrated into everyday business operations rather than limited to written procedures or the distribution of personal protective equipment.

3. The Role of Workers

Preventing occupational risks also requires the active participation of workers and their representatives.

Convention No. 155 includes provisions relating to cooperation, training, consultation and the reporting of dangerous situations.

Within an organization, workers should be encouraged to:

• Follow applicable safety instructions and procedures.
• Use work equipment and personal protective equipment correctly.
• Participate in training and preventive activities.
• Report hazards, incidents and situations that could cause an accident.
• Cooperate with employers and occupational safety representatives.
• Follow established procedures when facing serious and imminent danger.

However, responsibility for prevention must not be transferred entirely to workers. Employers retain the responsibilities imposed on them by applicable occupational health and safety legislation.

4. Relationship Between Convention No. 155 and ISO 45001:2018

Convention No. 155 and ISO 45001:2018 share several principles, including risk prevention, leadership commitment, worker participation and continual improvement.

However, they are different in nature. Convention No. 155 is an international labour instrument addressed to States that ratify it, whereas ISO 45001 is an occupational health and safety management system standard that organizations may adopt voluntarily or where applicable requirements call for it.

Their main areas of convergence include:

• Leadership: Management commitment to occupational health and safety policies and objectives.
• Worker consultation and participation: Involving workers in hazard identification and the improvement of preventive measures.
• Risk management: Identifying hazards, assessing risks and implementing control measures.
• Competence and awareness: Providing the training and information needed to perform tasks safely.
• Continual improvement: Evaluating performance and correcting weaknesses in the management system.

In ISO 45001:2018, worker consultation and participation are addressed in Clause 5.4, leadership in Clause 5.1, and improvement in Clause 10.

The PDCA cycle — Plan, Do, Check, Act — is a useful method for structuring continual improvement.

ISO 45001 certification can help an organization structure its prevention activities. However, certification alone does not guarantee the absence of accidents and does not replace compliance with applicable legislation.

5. Application in Morocco: Legal Status

Morocco is a member of the ILO and has ratified several fundamental ILO Conventions concerning, among other matters, forced labour, child labour, non-discrimination, freedom of association and collective bargaining.

In June 2022, the ILO recognized occupational safety and health as a fundamental principle and right at work. As a result, Conventions Nos. 155 and 187 became fundamental Conventions.

As of 25 October 2026, Morocco has not ratified Convention No. 155, according to the ILO’s official NORMLEX database. Morocco did, however, ratify Convention No. 187 on 14 June 2019, and that Convention is in force for Morocco.

The fact that Morocco has not ratified Convention No. 155 does not mean that occupational health and safety is unregulated in the country. Moroccan legislation already establishes requirements for the prevention of occupational risks.

Law No. 65-99 establishing the Moroccan Labour Code, promulgated by Dahir No. 1-03-194 of 11 September 2003, includes a title dedicated to occupational hygiene and worker safety, beginning with Article 281.

These provisions regulate several aspects of workplace prevention. They must be applied in accordance with the Moroccan legislation in force, independently of the country’s ratification status under Convention No. 155.

Moroccan companies should therefore integrate international prevention principles into their practices while verifying their national legal obligations and any additional requirements applicable to their industry.

6. Why Is Convention No. 155 Important for HSE Professionals?

For professionals working in health, safety and environment (HSE), Convention No. 155 is a useful reference for understanding the foundations of occupational risk prevention.

It helps professionals understand:

• The relationship between national policy and workplace prevention.
• The respective roles of employers and workers in risk control.
• The importance of training, consultation and participation.
• The need to integrate prevention into work organization.
• The relationship between legal obligations and occupational health and safety management systems.

These principles can support HSE training, internal audits, risk assessments and ISO 45001 implementation, provided that national legal requirements are clearly distinguished from international guidance and reference instruments.

Conclusion

ILO Convention No. 155 is a major international reference for developing occupational health and safety policies. It emphasizes risk prevention, employer responsibilities, worker participation and the improvement of working conditions.

Although Morocco had not ratified this Convention as of 25 October 2026, national legislation already establishes various obligations concerning occupational hygiene and worker safety. Companies must therefore comply with the Moroccan legislation in force and may use ILO principles and ISO 45001 to strengthen their prevention practices.

For HSE professionals, understanding Convention No. 155 helps place occupational prevention policies in their international context and supports the development of safer and healthier workplaces.

Official Sources and References

1. ILO — Convention No. 155 concerning Occupational Safety and Health and the Working Environment, 1981
   https://normlex.ilo.org/dyn/normlex/en/f?p=NORMLEXPUB:12100:0::NO::P12100_ILO_CODE:C155

2. ILO — Ratifications of Convention No. 155
   https://normlex.ilo.org/dyn/normlex/en/f?p=NORMLEXPUB:11300:0::NO::P11300_INSTRUMENT_ID:312300

3. ILO — Morocco: Ratifications and Non-Ratified Conventions
   https://normlex.ilo.org/dyn/nrmlx_en/f?p=NORMLEXPUB:11210:0::NO::P11210_COUNTRY_ID:102993

4. ILO — International Labour Standards on Occupational Safety and Health
   https://libguides.ilo.org/occupational-safety-and-health-en/standards

5. ILO — Convention No. 187 concerning the Promotional Framework for Occupational Safety and Health, 2006
   https://normlex.ilo.org/

6. Morocco — Labour Code, Law No. 65-99, Title IV on Occupational Hygiene and Worker Safety
   https://natlex.ilo.org/dyn/natlex2/r/natlex/fe/details?p3_isn=67319

7. ISO — ISO 45001:2018, Occupational Health and Safety Management Systems
   https://www.iso.org/standard/63787.html