Optical radiation protection in explosive atmospheres

IEC 60079-28:2025 defines the requirements for the protection of equipment and transmission systems using optical radiation in explosive atmospheres. This type of protection is relevant for Ex equipment, Ex associated equipment and Ex components that include optical systems, for example, lasers, optical fibre systems, optical sensors or other devices where optical radiation can be emitted into a hazardous area.

Optical radiation can become an ignition source when it is absorbed by surfaces or particles, causing them to heat up. In special cases, a strong focused laser beam can also cause direct breakdown of gas and create plasma, which may ignite the surrounding explosive atmosphere. For this reason, optical systems used in hazardous areas must be assessed not only as electrical equipment, but also with regard to the energy and behaviour of the emitted light.

The standard is used together with IEC 60079-0 and applies to all equipment groups and all Equipment Protection Levels. It covers optical radiation in the wavelength range from 380 nm to 10 µm. The protection concept may be based on inherently safe optical radiation “op is”, protected optical radiation “op pr”, or optical systems with interlock “op sh”.

The new 2025 edition is a technical revision of the 2015 edition. Among the main changes are a clarified scope for laser equipment, optical fibre equipment and focused optical systems, removal of the ignition test option, a new structure with type verifications and tests, a new subclause for optical detectors, clarification that calculations may be used for optical power assessment, and additional marking examples.

At SIQ Ljubljana, we also test and certify Ex equipment and components using optical radiation. Certification can be carried out in accordance with Directive 2014/34/EU (ATEX) and the international IECEx certification scheme.

More information:
Matej Debenc
E-mail: matej.debenc@siq.si
Tel.: +386 1 4778 227