It is obvious that a gas detector should be installed as close as possible to a potential leak of (combustible) gas or liquid which means it is almost always installed in Zone 1 / Division 1.

However, an optical device such as a flame detector, does not need to be that close and simply covers more area when installed at a distance of the potential leak. Within the usable detection range of a flame detector more than 80% of the applications are actually Zone 2 / Division 2 from the perspective of a flame detector.

So why invest in costly Zone 1 / Division 1 equipment, expensive installation and elaborate maintenance?