STK Testing: Which Devices, Which Intervals, Who May Test?
The safety technical inspection per §12 MPBetreibV — clearly explained for operators
What is the STK?
The Sicherheitstechnische Kontrolle (STK) — safety technical inspection — is a legally required test for certain medical devices. It is regulated in §12 of the Medical Devices Operator Regulation (MPBetreibV) and serves to ensure the safe condition and functionality of medical devices.
The STK should not be confused with the DGUV V3 test: While DGUV V3 tests the electrical safety of all equipment, the STK covers the entire safety-related function of medical devices — including mechanical, pneumatic, and software-related aspects.
Which devices require an STK? — Annex 1 MPBetreibV
The STK obligation applies to all medical devices listed in Annex 1 of the MPBetreibV. These include:
- Defibrillators (external and implantable, where testable)
- Infusion pumps and syringe pumps
- HF surgery devices (high-frequency surgery)
- Ventilators (incl. CPAP, BiPAP)
- Infant incubators
- Resuscitation devices
- Anesthesia machines
- Dialysis machines (hemodialysis, peritoneal dialysis)
- Heart-lung machines
- Lasers and high-energy light sources (medical class 3B and 4)
- Electrosurgical devices
- Pressure chambers (hyperbaric oxygen therapy)
- X-ray machines and CT scanners (unless covered by RöV)
Important: Devices that are not listed in Annex 1 can also become STK-mandatory if the manufacturer prescribes an STK in the instructions for use.
STK intervals: How often must testing be performed?
| Regulation | Interval | Note |
|---|---|---|
| Standard interval per §12 MPBetreibV | 2 years | Applies when the manufacturer does not specify a shorter interval |
| Manufacturer specification shorter | Manufacturer interval | Manufacturer specifications always take precedence |
| After repair / maintenance | Immediately | §7 MPBetreibV — testing before recommissioning |
| Initial commissioning | Before use | Functional test and instruction required |
The interval begins with the date of the last STK or, for new devices, with the date of commissioning. Exceeding the interval is not permissible — the device may no longer be used after the deadline until the STK has been completed.
Who may perform the STK?
The requirements for tester qualifications are regulated in §5 MPBetreibV. The tester must meet the following prerequisites:
- ✓ Suitable training: Electrical engineering or medical technology training with demonstrated expertise
- ✓ Relevant professional experience: Current practical experience in testing medical devices
- ✓ Suitable testing equipment: Calibrated measuring instruments that meet the requirements of the respective standard
- ✓ Independence: The tester must be independent in their professional assessment
- ✓ Current knowledge: Regular continuing education on new standards and regulations
Alexander Driller meets all these requirements: TÜV Süd certified for DIN EN 62353, registered with the HWK Karlsruhe (Chamber of Skilled Crafts), with current testing equipment and regular continuing education.
What is tested during an STK?
The STK comprises three consecutive testing steps:
1. Visual inspection
- ✓ External condition of the device (housing, cables, plugs, hoses)
- ✓ Completeness of all components and accessories
- ✓ Legibility of labels and warning signs
- ✓ Presence of the instructions for use
- ✓ Completeness check of the medical device log
2. Functional test
- ✓ All operating modes and programs function correctly
- ✓ Safety features (emergency stop, overload protection, alarms) trigger reliably
- ✓ Displays and screens are correct and legible
- ✓ Mechanical functions (movement, locking) work properly
3. Measurement-based control of safety-relevant parameters
- ✓ Protective conductor resistance and insulation resistance
- ✓ Leakage currents (housing, patient, touch)
- ✓ Device-specific parameters depending on type (e.g. leakage current for infusion pumps, energy output for defibrillators)
- ✓ Documentation of all measured values in the test report
STK vs. DGUV V3: When does a device need both?
The short answer: Very often. The STK and the DGUV V3 test have different legal bases and test partially different aspects:
| Feature | STK | DGUV V3 |
|---|---|---|
| Legal basis | §12 MPBetreibV | DGUV Vorschrift 3 / BetrSichV |
| Applies to | Annex 1 medical devices | All electrical equipment |
| Scope of testing | Entire safety function | Electrical safety |
| Standard interval | 2 years | 6–24 months |
| Testing standard | DIN EN 62353 + device-specific | DIN EN 62353 / DIN VDE 0701-0702 |
A defibrillator in a cosmetic studio (if present) needs, for example, both an STK every 2 years and a DGUV V3 test. A pure IPL device without CE marking as a medical device only needs the DGUV V3 — unless it becomes a medical device through MDR Annex XVI.
Cosmetic devices and STK: When does an IPL/laser device fall under the STK?
This question is becoming increasingly relevant through the MDR (EU Medical Devices Regulation) and its Annex XVI. Until now, most cosmetic lasers and IPL devices were not medical devices — and therefore not STK-mandatory.
This is changing: With the full implementation of MDR Annex XVI, products without a medical purpose that pose similar risks (lasers, IPL, high-energy light sources) will be subject to medical device regulations. For studio operators, this means:
- ✓ Cosmetic lasers of class 3B and 4 will likely become STK-mandatory
- ✓ IPL devices with high energy density could also be affected
- ✓ The exact implementing acts of the EU are still partially pending
- ✓ Regardless, the DGUV V3 obligation already applies to all these devices
STK and DGUV V3 in one appointment
Elektrotechnik Driller performs STK and DGUV V3 testing in a single appointment — saving time and costs. You receive a complete test report for each device that documents both tests. If defects are found, we can often perform a repair directly on-site.
Documentation: What must be retained?
After each STK, a test report must be created and filed in the medical device log. The report contains:
- ✓ Unique identification of the device (manufacturer, type, serial number)
- ✓ Date and result of the test
- ✓ All measured values with target/actual comparison
- ✓ Identified defects and their assessment
- ✓ Name and qualification of the tester
- ✓ Next testing date
The retention period is at least until the next STK, although we recommend retention for the entire service life of the device.
Commission STK testing
Have your medical devices professionally and punctually tested — in the Pforzheim, Karlsruhe, and Stuttgart area: