6. Illumination and photometric properties
Escape route signs, fire equipment signs and life saving appliance safety signs according to SOLAS regulations shall be of photoluminescent material illuminated by electrically powered lighting. The preferred lighting source for photoluminescent safety signs shall be indicated by the supplier accompanied by data on the luminance decay properties as a function of luminance and light source as given in ISO/DIS 17398 Durability of safety signs. The light source of an internally illuminated sign should provide a luminous contrast appropriate to its environment without producing glare. All internally illuminated signs shall be illuminated either at all times or illuminated externally under normal, non mains failure conditions and the minimum luminance of any area of the sign should not be less than 2cd/m2 under mains-failure conditions.
Where a sign is illuminated by an external source, the vertical illumination should be a minimum of 100 lux under normal lighting conditions and have a minimum of 5 lux with a uniformity of 0.7 under mains-failure conditions.
Illumination is required to ensure signs are legible and conspicuous. Effective illumination is required both in normal and in mains-failure conditions. It is not normally considered satisfactory to rely on daylight alone for satisfactory illumination. There are various ways of ensuring the satisfactory illumination of signs.
Some types of lighting, e.g. low pressure sodium, do not enable effective colour recognition nor activate photoluminescent signs adequately and are therefore unlikely to be suitable for the illumination of escape route signs.
Where emergency lighting is the source of illumination of the sign in the mains-failure condition, the response time of the emergency lighting should comply with IMO Regulations which provides also a minimum duration requirement for the emergency lighting.
Where a photoluminescent sign is used, the vertical illumination should be a minimum of 100 lux under normal lighting conditions. The luminance decay performance of the sign shall be no less than the minimum requirement as given in ISO 15370 for low location lighting and in all cases shall be no less than any photoluminescent low location lighting installed on board the ship.
(Note: The vertical illumination under emergency lighting conditions shall be a minimum of 5 lux with a uniformity of 0.7 under mains-failure conditions.)
8. SIGN SIZE AND VIEWING DISTANCE
The viewing distance of a sign is the maximum distance from which the sign has to be recogniseable and comprehensible.
Escape route signs should be both conspicuous and legible. The size of sign necessary to achieve these criteria will depend upon both the viewing distance and the illumination of the sign.
The viewing distance of an escape route sign is determined by its position within the primary escape route (i.e. signs should not be sized by their position within any alternative, secondary escape route).
Any variation of the sizes of signs within a ship should be kept to the minimum.
Smaller viewing distances will enable smaller sizes to be used whilst remaining conspicuous and legible.
Conversely larger viewing distances may reduce the number of signs required but increase their size. Signs that are larger than necessary may encourage an evacuee to travel a far greater distance to a place of safety than is necessary if the evacuee should mistake the intended primary escape route.
Within large open areas with multiple escape routes particular care should be taken to ensure that the signs are the appropriate size for the intended primary escape route.
The viewing distance of an escape route sign will be affected by the vertical illumination on the sign or its luminance in the case of an internally-illuminated sign. The lower the vertical illuminance (or luminance) the larger the sign will need to be for any chosen viewing distance as shown by the limits of Tables 1, 2 and 3 in appendix ?.
The maximum viewing distance, D, can be calculated from the overall height of the graphical symbol, as, by using the appropriate distance factor Z:
D = Z as (where as and D have the same units).
Distance factors for externally illuminated escape route signs under a range of different conditions of vertical illuminance are provided in Table 1. Distance factors for internally illuminated escape route signs with different ranges of mean luminance of the contrast colour white are recommended in Table 2. Both tables are based on the ISO7010 graphical symbol with a ratio of overall height of graphical symbol to width of critical detail of not greater than 15:1.
||Distance factor Z for externally illuminated escape route signs based on ordinary materials or photoluminescent materials. BS 5266-7 requires Z = 100 in the mainsfailure condition, based on the height of the sign.
|Vertical illuminance at sign (lux)
||Distance factor Z
|| Distance factor Z for internally illuminated escape route signs. (Note 1: If gaseous tritium signs are used Z = 50 may be accepted).
Emergency lighting standards often require Z = 200 in the mains-failure condition, based on the height of the sign.
|Mean luminance of white contrast colour cd/m2
||Distance factor Z
|| Examples of maximum viewing distances for externally illuminated escape route signs of different graphical symbol height subject to a vertical illuminance of 100 lux are presented in Table 3. The appropriate value for Z selected from Table 1 is 170.
|Graphical Symbol Height
|| 12.7 metres
|| 17.0 metres
|| 18.7 metres
|| 20.4 metres
|| 22.1 metres
|| 25.5 metres
9. CONSTRUCTION - DURABILITY AND SUITABILITY
Signs should be selected to be suitable for their operating environment.
Factors to be considered include:-
(i) Of base material.
(ii) Of graphical content.
(iii) Colour/light fastness.
(iii) Surface spread of flame.
(c) Fixings - type and suitability
Electrically powered signs should comply with appropriate standards for emergency lighting.
Installed signs should be suitable for the expected environmental conditions.
Installers and designers should seek adequate assurance from suppliers in these respects.
All signs shall be supplied according to ISO/DIS 17398 Durability of safety signs
10. SERVICING AND MAINTENANCE
Escape route signs should be cleaned and visually inspected at regular intervals and action taken to remedy any defects.
Signs required as part of the emergency escape lighting installation should be inspected, tested and maintained.
If the ship is modified or the use changes or if any of the design considerations detailed under 4.1 and 4.2 vary significantly, the escape route sign installation should be reviewed and modified as necessary.
11 Assembly station identification
12 Lifeboat station identification
13 Deck markings as part of escape path marking
14 Exit and emergency exit identification
15 Use of safety signs to facilitate door opening
16 Location of means of escape safety signs at high, intermediate and low location
17 Identification and signing of secondary escape routes