Explosive atmospheres - Part 28: Protection of equipment and transmission systems using optical radiation

IEC 60079-28:2025 specifies additional requirements for Ex Equipment, Ex associated equipment or Ex Components containing optical systems emitting optical radiation, which is exposed to explosive atmospheres. These additional requirements are applicable for all equipment groups and all Equipment Protection Levels (EPL).

This document contains requirements for optical radiation in the wavelength range from 380 nm to 10 μm. It covers the following ignition mechanisms:

？ Optical radiation is absorbed by surfaces or particles, causing them to heat up, and under certain circumstances this might allow them to attain a temperature which will ignite a surrounding explosive atmosphere.

？ In rare special cases, direct laser induced breakdown of the gas at the focus of a strong beam, producing plasma and a shock wave both eventually acting as ignition source. These processes can be supported by a solid material close to the breakdown point.

？ Annex A provides guidance when considering ignition mechanisms that influence the hazard of optics in explosive atmospheres.

This document applies to

a) laser equipment; and

b) optical fibre equipment; and

c) any optical system that converts ligh