Power outages are no longer a rarity even in highly industrialised countries.
In cases of power failure, the consequences given our fully-electrified and tightly networked industrial society are not only great economic damages but also accident hazards for people. For this reason, the European directive 89/654/EEC concerning the minimum safety and health requirements for the workplace stipulates that work places must be equipped with emergency lighting.
In Germany, this directive was incorporated into national law through the work place ordinance "Arbeitsstättenverordnung" of 12.8.2004 (last amended on 31 August 2015). The situation is similar in other EU countries.
The same applies for EU directive 92/58/EEC on the minimum requirements for the provision of safety and /or health signs at work (last amended
on 26 February 2014) which regulates the design of safety signs e.g. for escape routes, which have to remain operational in case of power failure using an emergency power supply.