Marriott Timed Egress Analysis


Provided fire and egress modeling as an AM&M to demonstrate an increase in occupant load for an office floor level.  The results from this analysis demonstrated that through the installation of automatic smoke detection, tenable conditions were afforded long enough for the excess occupants to safely egress.

The Approach

Performance Based Fire Protection Engineering, PLLC evaluated a high-rise office building, occupied by Marriott, against design fire scenarios in order to analyze the impact that the inclusion of smoke detectors would have on egressing occupants from the space.  The design team was proposing a maximum load of 338 occupants on this floor level, 46 occupants greater than the prescriptively allowed 292 occupants, as determined by the limited egress component width of the stairwells.  Through this analysis, the times to both smoke detection and sprinkler activation/waterflow were obtained from the simulated fire scenarios.  The time differential between these two conditions was then compared in order to determine if the RSET based off of smoke detection was less than the RSET based off of a waterflow condition, even considering the proposed increased occupant load.

Using this performance-based approach, we determined that the inclusion of spot-type smoke detection (with an occupant load of 338 occupants), installed throughout all areas of the floor level resulted in a RSET less than that calculated for the detection via sprinkler activation/waterflow (with an occupant load of 292 occupants) for all fire scenarios evaluated.  In an effort to limit smoke detection to corridor and common areas only, two fire scenarios further evaluated their respective fire events occurring in a compartmented room, with the door left open and no smoke detection within the compartment of fire origin itself.  This resulted in a delayed time to smoke detection due to the smoke plume being required to spill through the doorway and out into the common area, followed by traveling across the ceiling until it reached a conservatively spaced detector location.

Benefit to the Design Team

Based on the results of this analysis, spot-type smoke detection was determined to be required throughout the entirety of the floor level in order to provide an added level of life safety to egressing occupants, at the proposed occupant load which exceeds the capacity of the limiting egress component.  The end result was that the client was allowed to have the additional 46 occupants on this floor level.

Project details

  • Year: 2018
  • Project: Marriott Egress Analysis
  • Customer: HD Engineering
  • Benefit to the Team: Increase in Occupant Loading
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