The Effect of Evacuation Time on Fire Safety Management Planning in Two High-rise Residential Buildings

Population expansion in line with the rapid urban development, has resulted in the limitation of proper land for construction and the increase in the land values. This fact in one hand, and the advances in the construction industry in the other hand, lead the high-rise residential buildings to be the dominant type of settlement in Iran megacities such as Tehran and Karaj. High-rise residential buildings possess unique challenges in terms of fire safety that requires special attention to be given to safety management efforts. The limitations according to the means of egress for evacuation and fire service access in the time of fire emergencies, and presence of large number of occupants, properties and equipment in the building which increases the fire severity, are some examples. There are three key aspects that should be considered in any fire safety planning: 1) occupants and their attributes; 2) building physical aspects and installed equipment; 3) management and maintenance procedures. Despite suggestion of approaches such as elevator evacuation, or defend-in-place strategies for high-rise buildings, evacuation through the stairs is known as the ultimate way to provide safety and is required by Iran’s safety regulations.
This study examines the aspects of safety management for reducing loss and damage of fire events in two high-rise residential buildings based on evaluating the evacuation time-line for a similar scenario. Iran’s prescriptive fire safety code provides the requirements for components in the means of egress to acquire the optimal safety level. In this regard the concept of evacuation time is limitedly being known and utilized. Moreover, since it is argued that for each building/ occupants/ scenario, there would be a probable range of time that evacuation is more likely to take place in this period, by analyzing the evacuation time-line, the worst probable conditions for safety management planning could be determined. The methodology used in this research is based on field survey with a combination of quantity and quality data analysis. Field surveys based on checklist and preparing updated existing layouts, in addition to in-depth interviews with the management team, security and maintenance personnel, and fire safety experts provide the qualitative data for analyzing the building parameters and components of the exit route. In the next step, noticing that total evacuation time is consisted of two time periods which are delay time and movement time, each time period is calculated in several procedures, and the method that resulted the maximum amounts are considered as the reference for further analysis.
Findings indicate that the maximum delay time is obtained from the European confederation of fire protection association method that categorizes and ranks each building in terms of occupancy parameters and occupant’s status, alarm features, complexity of built-environment and management mechanism. These are called behavioral scenario categories and each rank is equivalent to an estimated delay time in evacuation. The maximum movement time is resulted from a formula which calculates movement time based on effective unit of exit path for each occupant in stairs and doorways, the densities in the stairway, and the movement speed. In calculation for both buildings, significant amount of total evacuation time was due to the delay time (78% for building A and 68% for building B).
It could be resulted that although life safety systems and equipment are installed in high-rise buildings, because of the improper maintenance of building and unfamiliarity of residents and staffs with the functions of these installations, and lack of a coherent pre-determined plan to response the emergency situation and assisting disabled occupants to egress, number of problems may occur during fire incidents which may result increasing delay time in evacuation time. The more delay time, the greater chance of saving occupants lives is wasted, so reducing delays in responding an emergency could be a critical priority in safety management. Higher amount of delay time results in lowering safe available time for travel period. From movement time calculations, it was achieved that during operation period, dominant use of elevators for vertical movements in high-rise residential buildings resulted the lack of consideration to the mobility of staircase for emergency situation and numerous obstacles were placed in stairs that resulted the lowering of effective exit width and movement speed. Safety management measures should ensure that the maximum available capacity of means of egress is not being lost in operation and maintenance. In addition since the elderly and children constitute a considerable part of the residential apartment occupants, in safety management planning, strategies should be made to avoid interference of slow movements of these people with the flow of others. Training occupants, evacuation drills and providing refuge areas if they are missing could be proper solutions. Finally it is proposed that Iranian building codes should be revised by noticing to the importance of evacuation time in architectural design of exit route.