NFPA Journal®, May/June 2008
By Christine Theisen and Richard Muller
Thirty-foot (9-meter) balls of flame indoors, entire stages that rise and fall, performers and props flying over the audience—it’s all in a day’s work in the theaters of Las Vegas, Nevada. That also means the building inspectors and fire marshals of the Entertainment Capital of the World are always facing new enforcement challenges.
Pushing the boundaries of the theatrical experience means that productions also push the boundaries of the building and fire codes and standards with which they must comply—and Las Vegas has some of the strictest building and fire codes in the nation. The city uses the 2006 edition of the International Building Code (IBC) and associated referenced NFPA standards, including those highly specialized documents that regulate flame effects and pyrotechnics.
Relying on communication with building and fire officials, and the creativity Las Vegas is known for, the theaters in Las Vegas present unique challenges that require unique fire protection solutions. The Las Vegas office of Rolf Jenson & Associates, Inc. (RJA) has designed fire protection systems for nine theaters:
As evidence of Las Vegas’ growth, RJA is currently designing another four theaters.
The schemes, themes, and audience environments are as much a part of the show as the performers themselves, and each venue presents a different challenge. The only constant is the question, “How can we push the envelope?”
A pathway to entertainment
Cirque du Soleil® performances — KÁ, LOVE, and Zumanity — begin in the lobby that patrons pass through to get to their seats, and each venue strives for a distinctive look or feel to set the mood or theme for the experience to come. In the lobby of the Cirque du Soleil production KÁ at the MGM Grand, for example, the architects and designers strove for that special creative mystique by proposing to use some materials that had not been tested for compliance with the interior finish guidelines of the Southern Nevada Building Code.
These materials included faux plant-like leaf elements and resin panels that were to be applied to the walls and ceilings. While the resin would be deemed compliant for wall application to a noncombustible surface, the resin in a ceiling configuration and the leafy elements extending from a wall or ceiling configuration would not.
For the leafy element, the concerns were that, once attached, they would extend out from the wall or the ceiling and the leaves could not be attached to a noncombustible backing. Potential degradation of the resin in the elements used on the ceiling during a fire was also a concern. As the elements melted, they could drip onto exiting occupants, and the melted remnants of the products could interfere with sprinkler operation.
To address these issues, the AHJ required that each product be tested separately according to NFPA 286, Fire Test for Evaluating Contribution of Wall and Ceiling Interior Finish to Room Fire Growth. The results of the tests of the two products were not favorable. They degraded well before the time limits set by NFPA 286. As a result, the leafy product was not used in the lobby, but the resin ceiling panels were reworked into a code-compliant solution by encasing the resin top and bottom in glass, which eliminated the degradation hazard significantly while keeping the designer’s intent.
Once inside the seating area, the audience uses the aisles to reach their seats. The aisles in a theater are one of the most critical life-safety portions of the seating area during an emergency because they must be able to deliver large numbers of people, who are typically unfamiliar with their surroundings, to the exits in an orderly and timely fashion. Thus, the proper arrangement and configuration of the aisles are essential. Stepped aisles must be uniform in height, width, and depth to prevent occupants from tripping and falling. The lighting levels of the aisles’ walking surfaces are also an important consideration. An improperly designed aisle could add anxiety to an already stressful situation.
Proscenium walls and openings
When the distance between the stage floor and the roof structure is more than 50 feet (15 meters), a fire-rated proscenium wall is required to separate the audience and the stage. Large openings in the proscenium wall are typically protected with a proscenium curtain intended to keep hot gases, flames, and smoke from a fire on stage away from the audience for 20 minutes. The proscenium curtain is also used to shield the glow of a severe fire on the stage from the auditorium for the same time period.
In the theater housing KÁ, theatrical equipment tracks are used to bring props and performers from the stage side of the proscenium to the seating side and back again through the top of the proscenium opening, making the use of a standard proscenium curtain impossible. The tracks prevent the use of an overhead opaque curtain typically used in conjunction with a water curtain. The size of the opening in the proscenium wall posed challenges, too: It is 56 feet (17 meters) high by 112 feet (34 meters) wide, totaling 6,272 square feet (580 square meters).
To make sure the fire-safety design and fire protection systems took these challenges into account, a water curtain without an opaque curtain was used between the stage and the seating areas instead of a proscenium curtain, and it was interlocked with a deluge sprinkler system installed above the stage at the gridiron level. To overcome the momentum of the hot gases and smoke and reach a fire on the stage, the system was provided with larger-orifice sprinklers to create larger water drops. A cross-zone detection system featuring flame detection and air sampling smoke detection is used to activate the deluge system. In this instance, activation of the deluge system does not occur until both detection modes are activated.
Since the water curtain itself might not prevent the flow of hot gases and smoke from the stage to the seating area, a smoke control system was designed to keep the smoke layer above the height of the proscenium opening. This system was designed to exhaust the space at a rate of approximately 337,000 cubic feet (9,550 cubic meters) per minute based upon a 10,000 BTU/sec fire, using makeup air from the seating area.
In the Jersey Boys Theater, the performers use a raised catwalk that extends from the stage out towards the audience, interfering with the closing of the proscenium curtain during an emergency. To make sure this doesn’t happen, the proscenium curtain upon release activates a switch in the curtain’s track near the upper section of the stage opening that causes a section of the catwalk to drop, allowing the curtain to pass through it without obstruction. Since the switch and the catwalk release are mechanical, they do not require power, monitoring, or supervision. Should a performer be on the audience side of the curtain when it drops, a means of egress is provided on the audience side so that the performer does not have to go back through the curtain to the stage.
The Southern Nevada Building Code requires that the proscenium walls be continuous from the foundation of the building to the roof, which can be something of a challenge when theaters are part of a mixed-use facility or are added to existing buildings or spaces previously used for other purposes. In the Planet Hollywood Casino and Resort, a theater housing the production of Stomp Out Loud was designed as shell space on the fourth floor that had no existing proscenium walls. However, Planet Hollywood was designed under the 1994 edition of the Uniform Building Code, which required occupancy separations. As a result of these separations, the floor assembly in the theater was designed with a 3-hour fire-resistance rating, and the AHJ approved a code modification that allowed the designers to terminate the proscenium wall at the 3-hour floor assembly. At this portion of the facility, the roof above the stage is the roof of the building, so the proscenium wall was designed to terminate at the roof as required by the code.
Theaters in the round
A theater in the round presents unique design and protection challenges. With the audience surrounding the stage, separating stage and audience is not a simple task and is not always practical. Take, for example, the theater that houses the LOVE production at The Mirage. The main stage has six symmetrically spaced pathways that converge at the stage, splitting the seating areas into six sections. The performers use the pathways to get to and from the stage throughout the performance. Because the stage is centrally located, strict code interpretation would require a proscenium curtain around the entire perimeter of the performance area. In lieu of standard proscenium protection, two deluge systems were installed to protect the main stage, while another three protect the six pathways. The stage deluge systems are activated by zoned flame detection and air sampling smoke detection systems, which are also zoned with deluge systems. Both detection systems have to be in alarm to activate their respective deluge systems.
The pathway deluge systems also have zoned dual detection systems that use pilot sprinklers and air-sampling-type smoke detection. For any deluge system to activate, it must receive a positive alarm status from both the pilot sprinklers and smoke detection systems in the associated zone.
Part of the stage at the New York-New York Hotel & Casino theater in which Cirque du Soleil presents Zumanity is arranged as a thrust stage, with audience seating on three sides. Originally, the proscenium wall was supposed to follow the curvature of the thrust stage, but it was redesigned so that the standard performance area, or the main stage, has a code-compliant proscenium separation from the audience. The thrust portion of the performance area is defined by the code as a platform, so separating it from the audience was not required. This saved Cirque du Soleil money and allowed it to perform without the boundaries that would have been required had a proscenium wall design been implemented.
Stage support access
Many Las Vegas theater arrangements try to use all the areas surrounding the performance area, known as the stage support areas, to the fullest extent possible. The fly lofts above and to either side of the stage do not have a great impact code-wise, but when the area below the stage is used as a stage support area, some additional considerations need to be taken into account.
The stage area of the LOVE production uses multiple lifts that move between the under-stage area and the main stage, and the space underneath the stage is used to store props and scenery. Because the stage is part of the 2-hour fire-rated floor assembly, it must be separated from the under-stage level. This protection, similar to the proscenium protection, was accomplished by combining a 2-hour floor assembly and water curtain protection. The 2-hour floor assembly and the lifts are similar to a proscenium wall and openings. At each floor opening underneath the stage, a draft curtain at least 18 inches (460 millimeters) deep is provided within a horizontal distance of 4 feet (1.2 meters) of the opening. A water curtain system with sprinklers located 6 feet (1.8 meters) on center was installed along each side of the draft curtain. The combination of the water curtain, draft curtain, and smoke control systems is designed to help keep hot gases and smoke from spreading to the stage.
Props and scenery are also stored backstage, where they are accessible through openings called vomitories, which are similar to proscenium openings and designed in a fashion similar to the stage lifts. To protect these openings, water curtains were provided at each opening on the backstage side of the vomitory, and draft curtains that are at least 18 inches (460 millimeters) deep are provided at the openings. The draft curtains are located within 12 inches (305 millimeters) of the water curtain to help the sprinklers activate. Since water curtains may not keep smoke from spreading across the vomitory, a smoke control system was provided for the backstage areas to minimize the flow of smoke and hot gases towards the audience.
The theater housing Zumanity also uses various traps and lifts as part of the performance. There are three traps in the main stage and four lifts in the platform that provide openings between the basement and the main level of the theater. Three of the four lifts in the platforms have sliding covers that move over the lift openings. Provisions for a 2-hour-rated floor separation at the lift openings was not possible, so the lift equipment rooms were constructed as rated assemblies to separate them from one another. This provides continuity of the proscenium wall and creates a fire-rated separation from the balance of the basement. As a result, the lift equipment room beneath the platform is considered part of the first-floor seating area, and the lift equipment room beneath the main stage is considered part of the first-floor stage. During normal conditions, the two lift equipment rooms have to be able to operate as one support area during the performance. Two pairs of 48-inch (1,200-millimeter) doors on magnetic hold-open devices and one 16-foot-wide (4.9-meter-wide) roll-down door provide the opening protection in the wall separating the two lift equipment rooms in an emergency.
Working with special effects
To “wow” the audience, many performances have special effects that may affect a theater’s life safety and fire protection systems.
In KÁ, for example, flame effects and pyrotechnics are used from the pre-show experience through the end of the performance. These effects include multiple balls of flame that rise as high as 10 to 30 feet (3 to 9 meters) and a lantern that produces a constantly burning open flame 18 inches (460 millimeters) in diameter and 30 inches (762 millimeters) high. Since these flames potentially increase the chance of a fire, manual override of the fire protection systems for the duration of the performance was not considered an option. Instead, a dynamic approach that permits intermittent bypassing of the detection components was used.
Since this theater’s deluge system and water curtain are activated by flame detectors and an air sampling system, a solution had to be found that would allow the use of the flame effects without changing the design of the life-safety systems too drastically. To prevent the unwanted discharge of water, RJA developed a system that was arranged to monitor the existing handsets of the stagehands responsible for indicating a “ready for activation” signal for an effect. The effects coordinator, who ultimately activates the effects from show control, must receive a signal from all stagehands and from the fire alarm system before activating the flame effects. The signal from the fire alarm system indicates that all handsets are ready for activation and that the detection systems have been successfully bypassed for the impending effect. Any release of a handset during an effect will prevent the effect from occurring and return the detection systems to active status. Should an alarm occur elsewhere in the theater, the flame effects control system will disable all connected flame effects and purge the fuel from the supply lines. Once the effect is concluded, handsets are released, and the alarm systems return to normal activation.
The AHJ accepted this solution since it limits the downtime associated with the protection systems, as well as the potential for human error.
During the performance of Phantom at The Venetian Casino Resort theater, four pieces of a large chandelier appear to “fly” together above the audience to become one complete chandelier. The challenge with this feature was coordinating the sprinkler system piping and components with the chandelier’s cabling system. If a sprinkler were to be in the path of a cable while the chandelier was coming together, it would be damaged and might release water.
Back to reality
Since most Las Vegas theaters are located adjacent to casinos, special consideration has to be given to the main exit, which is required in any assembly occupancy that can hold more than 300 persons. The Southern Nevada Building Code requires that the main exit be large enough to accommodate at least half the occupant load of the assembly space but not less than the required width of all means of egress leading to the exit. The main exit must also discharge onto a street or public way, which presents an issue since you enter and leave most Las Vegas theaters from a larger resort property without direct access to a street or public way.
During the development of the LOVE theater, the AHJ noted that the theater’s main exit did not meet the building code requirements for exit discharge onto a street or public way. However, the AHJ accepted the designers’ interpretation that the theater’s main exit did not have to discharge to the street since the theater is part of a mixed-use building, an issue the Southern Nevada Building Code did not address. The main exit was allowed to discharge into the casino.
The LOVE theater previously housed the Siegfried and Roy extravaganza, but underwent extensive renovation. The dramatically shaped theater once had code-compliant proscenium protection and seating, but during the renovation, the stage was moved to allow seating around all sides of the existing proscenium wall, creating a theater in the round. The theater is actually octagonal with two main entrances, each serving roughly half the respective seating area. Neither side of the theater can readily access the other.
To comply with building code requirements, each main exit can handle half the occupants for its respective portion of the theater. If the theater were a clock face, these exits would sit at eleven o’clock and one o’clock. The combination of the two main exits can handle half of the total occupants of the theater, as permitted when there is no clearly identifiable singular main entrance. The other exits that handle the rest of the occupants are enclosed stairwells, which are distributed evenly around the balance of the theater.
These are just a few examples of the design challenges encountered during the design of fire and life safety protection systems for Las Vegas theaters, each of which has a distinct configuration of seating and stage areas that require distinct fire protection systems to protect the audience and show personnel. So the next time you take in a show, enjoy the atmosphere and be assured that your safety is as important as your enjoyment.