In brief
Under Art. 8 of Law No. 6331, a very hazardous workplace must appoint an OHS specialist holding a Class A certificate, a hazardous workplace at least Class B, and a less hazardous workplace at least Class C. The certificate class rises step by step through training, examination and time actually worked in the lower class. A specialist whose certificate is below your hazard class does not count as an appointment of the qualification the law requires; you should therefore obtain the certificate class from your OSGB in writing and check it again whenever your class changes.
Class A, B and C OHS specialists: the short answer
The OHS specialist certificate comes in three classes, and each class determines the hazard class of workplace in which the specialist may serve. The basis for the Class A, B and C OHS specialist distinction is Art. 8/5 of Law No. 6331: to serve, specialists must hold a Class A certificate in very hazardous workplaces, at least Class B in hazardous workplaces and at least Class C in less hazardous workplaces. Art. 7 of the Regulation on the Duties, Powers, Responsibilities and Training of OHS Specialists states the same rule from the specialist's side.
| Certificate class | Workplaces where the specialist may serve |
|---|---|
| Class A | Less hazardous, hazardous and very hazardous: all workplaces |
| Class B | Less hazardous and hazardous |
| Class C | Less hazardous only |
The logic of the rule is simple: a higher-class certificate also covers workplaces in the lower classes; the reverse does not apply. What counts is not the specialist's title or experience but whether the certificate class matches your workplace's hazard class. If you do not know your hazard class, start with our article on how to find out your hazard class.
How is a certificate class obtained and upgraded?
Under the Law, OHS specialists are engineering or architecture graduates and technical staff who have been authorised by the Ministry and hold a certificate. Technical staff include technical teachers, physicists, chemists and biologists, as well as graduates of university occupational health and safety programmes. Art. 8 of the Regulation sets out how the classes are obtained. The main routes are:
| Class | Main route |
|---|---|
| C | An engineer, architect or technical staff member attends Class C training and passes the exam; graduates of occupational health and safety bachelor's programmes pass the exam |
| B | Documenting, through OHS specialist contracts, at least 3 years of actual service with a Class C certificate, attending Class B training and passing the exam; completing a master's degree in occupational health and safety or occupational safety and passing the exam |
| A | Documenting at least 4 years of actual service with a Class B certificate, attending Class A training and passing the exam; holding a doctorate in occupational health and safety or occupational safety |
The Regulation also provides separate routes for those who have served for certain periods in the inspection staff of the Ministry and related bodies. The conclusion for employers is this: a Class A certificate is usually earned over years of actual work in the lower classes and by examination. As a result, the supply of Class A specialists is more limited than that of Class B and C, and very hazardous workplaces need to plan early.
When is a Class A OHS specialist required?
A Class A OHS specialist is mandatory if your workplace's main activity is in the very hazardous class. Verified examples that are very hazardous in the list updated in 2025 under NACE Rev.2.1 include:
- 43.12.00 site preparation,
- 43.22.06 and 43.22.07 installation and maintenance of heating, ventilation and air-conditioning,
- 25.53.03 laser cutting of metals,
- 25.51.01 nickel plating of metals.
In a very hazardous workplace, the specialist's time is 40 minutes per employee per month, and one full-time specialist is appointed for every 250 employees. Additional appointments for further employees are calculated in minutes. To see the time required for your headcount, you can use the OHS obligations calculator.
Where can a Class B specialist work, and where a Class C specialist?
A Class B specialist can serve in hazardous and less hazardous workplaces. Common activities in Bursa's leading sectors, such as automotive supply, metal, furniture and weaving, are in the hazardous class; in the 2025 list, for example, 29.32.20 manufacture of parts and accessories for motor vehicles, 25.53.01 machining and welding work, 31.00.01 manufacture of furniture and 13.20.16 cotton weaving are hazardous. In these workplaces the specialist must hold at least a Class B certificate; a specialist with a Class A certificate may also be appointed.
Places where a Class C specialist can work are limited to less hazardous workplaces. In the 2025 list, for example, 62.10.00 software, 69.20.02 accounting, 70.20.01 business consultancy and 14.21.01 outerwear (garment manufacturing) are less hazardous. While a Class C certificate is sufficient for a garment workshop, if the same company starts weaving its own fabric and weaving also becomes a main activity, the class rises to hazardous and it can no longer continue with a Class C specialist.
Consequences of a lower-class specialist working in a higher class
When the match between specialist class and hazard class breaks down, the result is an administrative fine. Art. 26/1-b of Law No. 6331 provides a fine for each person not appointed against an employer who does not appoint an OHS specialist of the qualification set out under Art. 6, and the same amount applies for each month the breach continues. A specialist whose certificate does not suit the hazard class does not count as an appointment of the qualification the law requires.
The base amount for 2026 is 111,263 TL per person, and this fine is increased according to the size and hazard class of the workplace. Two examples:
| Situation | Calculation | Monthly amount |
|---|---|---|
| Hazardous workplace with 30 employees, Class C specialist | 111,263 TL × 1.5 (10–49 employees, hazardous: +50%) | 166,894.50 TL |
| Very hazardous workplace with 60 employees, Class B specialist | 111,263 TL × 3 (50+ employees, very hazardous: +200%) | 333,789 TL |
The calculations are examples; they repeat every month as long as the breach continues. You can calculate your own situation with the OHS administrative fines tool.
A mismatch usually arises not from a deliberate choice but from a change:
- The hazard class changed. The list was updated, or a very hazardous main activity was added to the workplace. When the class changes, the requirements of the new class must be met within 90 days; for details see our article on hazard class changes under NACE Rev.2.1.
- The specialist changed. During leave, resignation or an internal change at the OSGB, the certificate class of the replacement specialist was not checked.
- Several workplaces were mixed up. The same specialist was considered for the same employer's less hazardous office and hazardous production plant.
How do you ask your OSGB for the certificate class?
Do not rely on verbal assurances about the certificate class. Put it in writing with these steps:
- At the quotation stage: Ask for the quotation to state clearly your workplace's hazard class and the certificate class of the specialist to be appointed accordingly.
- In the contract: Have the name, certificate class and certificate number of the specialist to be appointed written into the contract. Add a clause stating that if the specialist changes, the replacement will hold at least the same class. For other clauses a contract should contain, see our article on OSGB contract clauses.
- At ISG-KATİP approval: Before approving the contract on ISG-KATİP (the Ministry's online OHS registration system), check that the appointed person is the specialist named in the contract. We explain how to check appointments in our article on checking appointments on ISG-KATİP.
- Verify the certificate: Check from official records that the specialist's certificate is valid and what class it is; for the method see our article on verifying an OHS specialist's certificate.
- File it: Keep a copy of the certificate in your OHS file; it is one of the first documents requested during an inspection.
- Repeat on change: Carry out this check again from the start whenever your hazard class, main activity or specialist changes.
You can request this information from any OSGB you work with, and from us for our OHS specialist services. You can find what the specialist should do in your workplace in our article on the duties of an OHS specialist.
Frequently Asked Questions
Can a Class C specialist work in a hazardous workplace?
No. Under Art. 8/5 of Law No. 6331, a specialist with at least a Class B certificate is appointed in a hazardous workplace. A Class C certificate is valid only in less hazardous workplaces.
Can a Class A specialist serve in a less hazardous workplace?
Yes. A Class A certificate covers all hazard classes. Because the Law says "at least C" for less hazardous workplaces, specialists with Class A and B certificates may also be appointed.
How many years of work are needed to obtain a Class B certificate?
Under the Regulation, a person who documents at least 3 years of actual service with a Class C certificate through contracts, attends Class B training and passes the exam obtains a Class B certificate. There is a separate route for those who complete a master's degree in occupational health and safety or occupational safety and pass the exam.
My hazard class has gone up; do I have to change my specialist immediately?
In a workplace whose hazard class changes, the obligations of the new class must be met within 90 days. If the current specialist's certificate does not suit the new class, a specialist of the appropriate class must be appointed within this period.
A certified specialist matched to your hazard class: site inspections, approved logbook, training plan, annual plan and report follow-up.
Bursa SİSTEMER OSGB Technical Team — written from the field experience of our OHS specialists and workplace physicians. Legal information is valid as of the publication/update date; contact us for an assessment specific to your business.