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Evacuation illumination is to ensure people evacuation from the building
when there is an emergency shutdown of working illumination.
The minimal illumination is 0.5 lx indoors and no less than 0.2 lx in opened
areas.

9.7 Artificial Illumination Sources

There are different types of lamps as sources of artificial illumination
depending on the light extraction element (Figure 9.4).

Figure 9.4 - Types of lamps as sources of artificial illumination

Incandescent, discharge and LED lamps are widespread as artificial
illumination sources.
Incandescent lamps are characterized by simple construction and production,
low price, easy exploitation, wide voltage and power ranges (Figure 9.5).
When solids and liquids are heated, they emit visible radiation at temperatures
above 1,000 K; this is known as incandescence.
Such heating is the basis of light generation in filament lamps: an electrical
current passes through a thin tungsten wire, whose temperature rises to around 2,500
to 3,200 K, depending upon the type of lamp and its application.

There are next drawbacks of incandescent lamps:
- high brightness (dazzle effect);
- low light efficiency (7–20 lm/W);
- relatively low operation life (to 2.5 thousand hours);

- yellow–red rays domination comparatively with natural light;
- high reheat temperature (to 140 °C that makes them fire hazardous).

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