What good are enclosed elevator lobbies?
Can performance criteria be written in understandable and enforceable language to be integrated into building and fire codes?
By Douglas H. Evans, PE, FSFPE, Clark County (Nevada) Building Department
For almost 40 years, enclosed elevator lobbies have been required by building codes adopted throughout a large portion of the United States. These protected spaces are primarily intended to limit smoke migration from floor to floor and increase the level of protection needed for occupants in multi-story buildings. They are also used to fulfill other functions, such as fire department staging operations.
During code development hearings for the 2015 International Building Code, there were a number of proposals to substantially eliminate enclosed elevator lobbies. The proponents of the deletion cited technical analyses and the absence of losses to justify reduction of this additional level of protection.
After consideration, I realized that the proponents of this deletion have some valid points. If fire/smoke growth/spread is limited by building components (compartmentation), automatic sprinklers, combustible loading (type and size of fuel packages), or other means, elevator lobbies may provide little to no additional benefit.
Let’s consider the following aspects that reduce the need for enclosed lobbies.
Having specialized in coordinating fire protection for the mega-resorts on the Las Vegas Strip for the past 20 years, my primary concern is a large open space with substantial fuel loading within the same environment as the elevator landing. This concern need not be limited to a casino; it could be an open office plan, retail sales floor(s), convention spaces, or any other reasonably large open space on any floor with sufficient combustible load to allow fire to propagate throughout the open space. In any of these scenarios, the only standard protection measure that can limit fire growth to the extent enclosed elevator lobbies may not be necessary is automatic sprinklers.
How dependent on automatic sprinklers is it reasonable to be? The failure rate of automatic sprinklers normally cited these days is around 10%. An additional concern is that sprinkler-controlled fires can still generate substantial quantities of smoke. Those of us who participate in code development are the voice of the public and must consider if it’s reasonable to accept that 9 out of 10 fires in large open areas containing sufficient fuel don’t need the additional protection provided by enclosed elevator lobbies. Over the years, there have been a number of non-sprinkler limited fires that have contributed to horrendous fire losses all over the world. Disregarding these losses is in essence “rolling the dice.” The question is not if a major life loss fire will occur where enclosed elevator lobbies would have helped—it’s when.
Limiting fuel loading is an ongoing maintenance issue. Combustible fuels may only be transient, but still must be considered and can create a fire hazard. In most instances it will be difficult, if not impossible, to limit combustible loading sufficiently to protect against the concern outlined here.
How about separating the elevator landing with building components that are capable of keeping fire and smoke away from the hoistway? Isn’t that what elevator lobbies are intended to do? A number of design approaches can provide the intent of enclosed elevator lobbies without incorporating additional compartmentation into the building. These may include a combination of separating the elevator landing from contiguous fuels with rated construction, limiting the size of the space the elevator opens onto, and limiting the fuel load in that space.
It’s apparent to me that enclosed elevator lobbies, in one form or another, provide a prudent level of protection to help restrict heat and smoke from entering the hoistway and migrating from floor to floor. Instead of asking if enclosed elevator lobbies are needed, the appropriate question is: How can the performance criteria included here be written in understandable and enforceable language that can be integrated into building and fire codes?
Douglas H. Evans is the fire protection engineer for the Clark County (Nevada) Building Department. Evans’ knowledge of fire protection includes suppression systems, detection and alarm systems, elevators, fire-resistive construction, exiting, hazardous materials, fire testing, fire modeling, secondary power supplies, and an understanding of the appropriate codes and standards. He is a member of the Consulting-Specifying Engineer editorial advisory board.