Deployable Fire- and Smoke-Protection Solutions

A closer look at the space-savvy systems delivering safe and code-compliant interiors
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Sponsored by Smoke Guard
By Jeanie Fitzgerald
Enclosed Elevator Lobby

As the name suggests, an enclosed elevator lobby is a room that is built around the elevator doors that can be closed off from the rest of the floor in the event of a fire. The code requires that these lobbies be constructed with walls that have a 1-hour fire rating and doors that have a 20-minute fire rating. The IBC also requires that the walls and doors resist the passage of smoke. The doors or opening protectives must meet the air-leakage performance criteria as outlined by the Underwriters Laboratories (UL) 1784. This test examines the rate that air and smoke leak from one side of the door to the other, and products and door assemblies that pass UL 1784 will appropriately resist the spread of smoke. Doors that have passed the UL 1784 test will receive an S Label.

To meet the fire- and smoke-protection requirements, architects commonly specify fire-rated swing doors that have earned an S Label. These swing doors typically have gaskets, so when the swing doors close, the gasket fills in the empty space between the door and the frame, creating a seal that prevents smoke from leaking out of the vestibule. The enclosed elevator lobby becomes a barrier on the fire floor that keeps smoke from penetrating the elevator shaft and, simultaneously, prevents smoke from migrating out of the elevator shaft onto a non-fire floor.

While an effective smoke partition, the enclosed elevator lobby is space intensive and places parameters on the design that can hinder an architect’s vision, especially in this era of open space. Incorporating enclosed elevator lobbies onto every floor connected by the hoistway requires that a lot of square footage be set aside for use if a fire event occurs, and that amount of space may be able to create a tremendous amount of value if employed another way. A different solution may allow an architect to add one more hotel room or hospital room to the floorplan, or create larger condos, generating more revenue for the building owner from the same footprint.

Elevator Shaft Pressurization System

Elevator shaft pressurization is a code-compliant alternative to the enclosed elevator lobby. This solution is designed to prevent smoke from flowing through an elevator shaft and affecting additional floors during a fire.

Elevator pressurization systems create and maintain a pressure differential between the hoistway and the adjacent elevator landing using large fans to inject large quantities of air into the elevator shaft. With the pressure differential that is created, smoke cannot enter the hoistway or move freely from floor to floor. While many consider elevator pressurization to be a simple and straightforward fan and ductwork solution for smoke control, these systems are incredibly complex. IBC Section 909.21 describes all of the requirements that must be met by the shaft pressurization system.

While elevator shaft pressurization is a more space-savvy smoke-protection solution, it is not a plausible solution for every type of project. Building characteristics such as height, shaft size, and the number of elevator cars in the system must be considered to determine if elevator shaft pressurization is a good fit. In addition, outside temperatures can affect the pressure inside a building. For example, the stack effect, which occurs when the bottom floors are in positive pressure and the upper floors are in negative pressure, and explains how smoke from a first floor fire migrates quickly up the shaft to spread throughout higher floors, can be materially changed during different times of the year. On hot summer days, this stack effect can be reversed due to positive pressure on the top floor and negative pressure on bottom floors, causing smoke from a fire on a roof or top floor to be sucked down through the building and into the lower floors. Designing a pressurized system that will work despite changes in climatic conditions is very difficult.

Please note that while elevator pressurization does help to prevent vertical smoke migration in the shaft, it is not an approved means of transforming an elevator door that is not smoke rated into a smoke-rated door. Where smoke-rated doors are required by code, smoke-rated doors must still be installed.

Additional Smoke-Rated Door

Another solution that can be used to prevent smoke migration at the elevator hoistway in lieu of an enclosed elevator lobby is to mount an additional smoke-rated door at the elevator opening. In many cases, this additional door is described as a gasketed swing door that has been tested in accordance with UL 1784 without an artificial bottom seal for air leakage and is equipped with am undercut drop-down seal and a closer, a device that pulls the door closed when the magnetic hold-open releases. These swing doors can be opened from the elevator car side without the use of a key, tool, knowledge, or special effort, ensuring that if people are in the elevator and the swing doors deploy, people will not be trapped inside. Most states also have elevator codes (ASME A17.1 2013 or newer) that also require a vision panel if a solution like this is used.

Here is how this type of door is designed to work in the event of a fire. In response to a local fire alarm, the magnetic hold-open releases, and the smoke-rated door swings closed over the fire-rated elevator door, providing the code-mandated fire- and smoke-rated barrier necessary for the space. The gasketing along the jamb of the door assembly fills in the space between the swing door and the door frame, creating a seal that prevents smoke from trespassing through it.

While this type of solution offers the smoke protection demanded by the code, there are a few shortcomings that should be considered before moving forward with smoke-rated swing doors on a project. Aesthetically, swing doors parked on the side of an elevator door are not a clean and modern look, and if there are more than two adjacent elevator doors, the hoistways may need to be spaced further apart to accommodate the placement of the open swing doors, which would require a supersized shaft. Also, swing doors are often wedged open by tenants or inadvertently blocked by furnishings on the floor. If these systems are unable to properly close, they are useless as a smoke barrier.

Luckily, there is another type of product that can offer the level of smoke protection required at the elevator door that does not have the aesthetic and functional limitations of the swing door solution or the space needs of the enclosed elevator lobby.

New Smoke-Rated Solution for Elevators

A rolling magnetic gasketing system protects elevator openings and the shaft from vertical smoke migration. It does this by creating a code-compliant smoke- and draft-control assembly when paired with a common fire-rated elevator door. The system deploys a reinforced, transparent, polymide film down over the shaft door when smoke is detected in the area. The edges of the film are equipped with flexible magnetic strips that adhere to the 2-inch-wide ferrous metal rails on either side of the doorway, providing a virtually airtight seal.

A rolling magnetic gasketing system deploys a reinforced, transparent film over the fire-rated elevator door in a way that creates an airtight seal and provides the smoke protection required by the IBC.

The IBC recognizes the combination of the normally fire-rated elevator hoistway doors and the rolling magnetic gasketing system, which creates an airtight seal over the shaft door, as an approved alternative for an enclosed elevator lobby. The fire-rated elevator doors provide the requisite fire protection, and the UL 1784-tested rolling magnetic gasketing system provides the necessary smoke protection.

Here is how it works. The gasketing system is installed at the elevator opening and integrated with existing fire-protection systems. The release mechanism of the system is connected to the UL-listed smoke detector required by code at the elevator landing. When smoke is detected, the release mechanism deploys the smoke-rated material over the elevator opening. The system is described as a fail-safe device that is gravity deployed, so once released, the film will only stop when the curtain assembly encounters the floor. After the emergency has passed, the screen can be rewound into the housing by activating a switch.

In terms of how this system is incorporated into an elevator opening aesthetically, architects have a few options. The housing that contains the smoke-rated material can be mounted directly above the elevator door frame or more discreetly in the ceiling or valence above the elevator door. The metal rails that flank the elevator opening can be painted to match the interior or left as unpainted stainless steel.

One notable advantage of this technology over others is that these systems offer deployable containment that is activated where fire and smoke are detected, allowing building occupants more time to egress the building.

 

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Originally published in Architectural Record

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