BS 5266-1:2006 5.2 Illumination for safe escape – Emergency escape lighting Further guidance is given in BRE Information Paper 9/97 [28], which identifies conditions that benefit from a minimum illuminance of 3 lx on the centre line of the escape route. 5.2.9.1.2 Colorimetric and photometric characteristics c) Externally illuminated escape route signs. Externally illuminated escape route signs should meet the colorimetric and photometric requirements of BS ISO 3864-4:2011, Table 1. During emergency lighting conditions, the illuminance on any part on the face of externally illuminated escape route signs should be not less than 5 lx. NOTE 4 For externally illuminated escape route signs, the value of distance factor of 100 given in BS EN 1838:2013, 5.5 is applicable when the vertical illuminance on the sign is at least 5 lx. PPA104 中文: https://www.hkfsd.gov.hk/chi/source/licensing/ppa_104_a.pdf 英文: https://www.hkfsd.gov.hk/eng/source/licensing/ppa_104_a.pdf