BS EN 1838: 2024 - Lighting Applications - Emergency Lighting for Buildings

A safety sign showing the location of an emergency exit or escape route must be visible from every point along the escape route, positioned so that anyone moving towards it is directed to an emergency exit.

New in 2024: in buildings or areas where occupants are not familiar with the layout, such as shops, hotels and offices with visitors, escape route safety signs must be operated in maintained mode, so they are lit at all times.

All safety signs and supplementary arrow signs needed during an emergency evacuation must meet ISO 3864-4 (photometric) and EN ISO 7010 (design). Their design principles and colours must follow ISO 3864-1, ISO 3864-3 and ISO 3864-4. Signs must meet these requirements under all conditions, both when the normal power is on and when it has failed.

All signs, and escape plans (ISO 23601), need internal or external illumination so they are conspicuous and easy to identify. Under both mains and emergency conditions, the safety colour green must stay green and the contrast colour white must stay white, within the colour boundaries in ISO 3864-4.

Adaptive safety signs complying with CEN/TS 17951 may also be used. These signs work with the emergency luminaires to show an alternative escape route, or to show that a route is closed.

Illumination of Safety Signs.

Safety signs can be internally illuminated (complying with EN 60598-2-22) or externally illuminated by an emergency luminaire complying with EN 60598-2-22.

• Internally illuminated signs: in emergency mode, the sign must provide a luminance of at least 2 cd/m².

• Externally illuminated signs: in emergency mode, the sign must receive a vertical illuminance of at least 5 lx.

• The ratio of maximum to minimum luminance within either the white or the safety colour must not be greater than 10:1, and large variations between adjacent points should be avoided.

• The ratio of the luminance of the contrast colour (white) to the safety colour (green) must be no less than 5:1 and no greater than 15:1.

• The minimum duration of illumination for escape route safety signs is 1 h. In the UK, BS 5266-1 normally calls for 3 h in most premises.

• Signs must reach at least 50% of the required luminance within 5 s and full luminance within 60 s.

• Where ambient light levels are high and the normal power is on, increasing the illumination of escape route signs should be considered to keep them visible.

• Sign luminance must be checked periodically, in line with BS EN 50172:2024 clause 7.4, to allow for ageing light sources and batteries and the build-up of dirt.

Viewing Distance.

An internally illuminated sign can be identified from further away than an externally illuminated sign of the same size. The maximum viewing distance is found using this formula:

l = z × h

where:
l is the distance of observation
h is the height of the sign (the size of the sign, not its mounting height)
z is the distance factor (100 for externally illuminated signs; 200 for internally illuminated signs)

*l and h must be in the same units.

For example, an internally illuminated sign 150 mm high can be identified from up to 30 m away, but an externally illuminated sign of the same size only from up to 15 m.

Mounting Height.
Where practicable, escape route safety signs should be positioned between 2 m and 3 m above floor level, measured to the base of the sign.

In large, high open areas it can make sense to mount signs above surrounding obstructions. In that case, a sign should be no higher than 20° above a horizontal eye height of 1.5 m when viewed from the maximum viewing distance.

Additional emergency exit signs for people with walking impairments may be mounted below 2 m.