Long evacuation time during emergency for offices in super tall commercial buildings is a deep concern and was discussed in this paper . Different codes and reg ulations for safe egress were reviewed. A building of fixed floor area but height s varying up to 500 m was taken as an example . The required total evacuation time s for selec ted offices in this building were estimated by four different empirical expressions . The height, population density and stair width of the super tall building were varied during the calculation . The estimated evacuation times were justifi ed with reference t o the local codes on means of escape . Even with a lower population density of 4.5 p ersons per square meter , which is only half of the allowed value specified in the Hong Kong code, the estimated minimum total evacuation time was 26.9 min. The evacuation ti me for a super tall commercial building with high occupant loading is very long. Evacuation by elevator is recommended to be an alternative . Safe evacuation strategy for supertall buildings should therefore be watched carefully . Keywords : evacuation time, super tall building, occupant loading , stair width 3 1. Introduction Hong Kong changed from an industrial city to a big international financial centre in the past three decades. I nstead of working in manufacturing plants, most of the employees in Hong Kong are working in offices now. Safety at non -industrial workplaces like office s, especia lly those in super tall buildings, is a concern . According to the Council on Tall Buildings and Urban Habitat [1], a supertall building is taken to be of height over 984 feet or 300 m. Evacuation has been identified as a key fire safety concern of supertall buildings [2]. Occupants are supposed to leave the fire room to a safe place with minimum injuries and life loss [ 3]. The fire codes on safe egress are frequently updated . Taking Hong Kong as an example, codes [4,5] specifying minimum requirements on hard ware fire safety provisions had been c hanged several times since 1972 . Offices in various types of buildings with different heights and ages would have very different egress problem s during emergency. For example, most of the buildings constructed before 1 972 have only one staircase . The flat inside used to be partition ed into smaller room s by timber products without fire retardant. Escape route s in exist ing buildings should be evaluated carefully. Evacuation time for offices in a super tall commercial building was studied in this paper . Code requirements on ensuring evacuation of occupants to a safe place through the protected corridor, passageways or lobbies within a certain period of time wer e review ed. Some k ey parameter s in Hong Kong codes are adopted f rom UK practices . Examples [6] are the nominal clearing time of 2.5 min for non -sprinklered buildings and 5 min for sprinklered buildings , and the discharge rate of 40 perso ns per minute per 5 00 mm exit width. Adequacy of such code for fire safety was discussed. Problems identified on evacuation w ere studied using empirical equations as reviewed 4 [7-9]. This study extend ed the previous project s [10] on evacuation times by empi rical expressions for offices in five tall buildings including a community building , a university campus, a commercial building , a bank and a residential building . The data of the commercial building plan were taken out from th at earlier survey [10]. The height of the building was varied as 100 m, 200 m, 300 m, 400 m and 500 m to inves tigate changes in evacuation time with height of the supertall building. The population density and the stair width of the building were also varied within the range specifi ed in the standard requirements with reference to the local codes. Sensitiv ity stud ies on the predicted evacuation time of the different empirical expressions by varying the stair width and population density of the building were carried out . Requirement s for emergency evacuation in offices with reference to the regulations in Hong Kong [4,5] were compared with those in the United States [ 3] and Australia [ 11]. The code of practice for Means of Escape (MoE) and Mean s of Access (MoA) [4,5] in Hong Kong , Nation al Fire Protection Association – Life Sa fety Code [3] in the United States , and the Building Code of Australia [11] in 1990 were taken as the