AN APPLICATION OF PERFORMANCE BASED CONCEPTS AT THE 

STRATOSPHERE TOWER, LAS VEGAS NEVADA 

By: 

James R. Quiter, P.E., Senior Vice President 

Rolf Jensen & Associates, Inc. 

INTRODUCTION 

This paper discusses the performance based approach to fire protection that was used at 

the Stratosphere Tower in Las Vegas, Nevada. It includes a description of the building, 

some of the problems faced, the analyses conducted and the solutions proposed and 

implemented. The building is now open and occupied, and is a major new landmark on 

the Las Vegas skyline. 

The Stratosphere Tower is the tallest free standing observation tower in the United 

States. It is 1,149 feet high. It contains several occupied floors including wedding 

chapels, function rooms, restaurant and lounge, and observation levels. At the top are 

two ride levels, which include an outside roller coaster and the Space Shot. Figures 1 

and 2 show typical floors of the tower. 

This paper identifies many of the problems that needed to be resolved in the design of 

the tower. However, it concentrates on the solutions used for evacuation of the building. 

ISSUES TO BE ADDRESSED 

In developing the fire protection program for a building such as the tower, there are 

many issues that had to be addressed. The most obvious issue is how to evacuate the 

building. The lowest occupied floor is 795 feet above grade. The area of the shaft is not 

large enough to provide remotely located stairs, and the height of the building makes the 

use of stairs as an evacuation route a less than perfect solution. 

A second problem was how to determine the occupant load in the tower, and how to 

limit that load. 

Third, the height of the tower had to be considered in evaluating fire fighter access and 

methods. 

Fourth, each utility, be it fire protection or other utilities, had to be specifically evaluated 

to assure reliability and safety. This includes all of the typical fire protection features 

such as water supply, fire alarm, smoke control, and emergency power. It also includes 

protection of gas lines that serve cooking equipment in the tower and use and shut-down 

of the rides at the top of the tower. 

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Lastly, the program needed to evaluate exposures to the tower from the structure below. 

The tower rises above a casino building and the impact of a fire in the casino had to be 

evaluated. 

THE EXIT, PROGRAM 

As stated previously, the tower presented specific problems with relation to evacuation of 

the building. Because some floors of the building may include occupancy by more than 

500 people, strict code application would require three exit stairs leading from the top of 

the tower to the base of the building. However, as with other observation towers, the 

shaft of the structure is not large enough to contain three exit stairs. Even with multiple 

stairs in the shaft, separation of those stairs would be impossible. Therefore, an alternate 

method of evacuating people was developed. 

The primq evacuation method for this building is the use of typical exit stairs for the 

occupied floors discharging to areas of refuge on the lowest two floors of the pod. In 

other words, from Floors 3 through 10 of the pod, three exit stairs are provided, enclosed 

in 2-hour construction, just as would be found in any other building. However, these 

stairs discharge to an area of refuge at the lowest two levels of the pod, which is still 750 

feet above grade. These two areas of refuge are used for no other purpose, and are 

completely non-combustiile. Rather than rely on mechanical systems to maintain them 

free of smoke in the event of fire, the two areas of refuge are open to outer air so that 

natural ventilation of these levels occur. Since the two areas are below the occupied 

levels, it is unlikely that fire in an occupied level would spread to the areas of refuge. 

With all the other fire protection systems provided, the possibility of fire spread is 

virtually eliminated. See Figure 3 for a layout of one of the areas of refuge levels. 

From the area of refuge, a single stair leads down through the shaft of the tower to 

grade. The primary evacuation route Erom the area of refuge involves the elevators. 

These elevators are two-level elevators which travel at 1,800 feet per minute and can 

discharge either within the main casino or at two specially designed discharge levels at 

the roof of the base building. These discharge levels are enclosed in two-hour 

construction from the roof to grade, and are separated from all other areas by two-hour 

construction. 

SPECIAL ELEVATOR PROTECTION 

In order to assure safety of the elevators, special protection was provided in the building. 

This building design was occurring during many of the NIST studies regarding use of 

elevators for evacuation in buildings. Many of the NIST recommendations, that were 

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developed in symposiums and through research on the use of elevators, were 

incorporated into this design. Some of these include the following: 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

Elevators open into two-hour elevator lobbies on all floors, both at the top and at 

the bottom of the building. 

There are four elevators which travel through the shaft from the base to the top. 

These elevators are served by two independent elevator machine rooms. The 

elevator machine rooms are separated by two-hour construction and have a 4-inch 

curb installed between them so that waterflow in one machine room will not 

impact the other machine room. 

Elevator lobbies are on a separate smoke control system to maintain 

pressurization with relation to adjacent spaces. Therefore, fire in an adjoining 

area will not spread smoke into the elevator lobby. 

Openings into the elevators are slightly raised from the remainder of the floor. 

Therefore, water flow on a floor level will not spill into the elevator hoistway 

because of the raised entry. 

Because the areas of refuge are at the two lowest levels of the pod, the elevators 

will not need to travel past a fie floor. Elevators will travel only between the 

areas of refuge and the base building. NOTE: Areas of refuge for disabled 

persons are provided within the enclosed pressurized stairwells at each level. 

Elevator shafts are vented to the outside at the top and the vents are separate 

from the machine rooms. In addition, the machine rooms are on separate smoke 

control systems and air conditioning for the machine rooms is on emergency 

power. 

All four elevators are on emergency power. The emergency power riser is in a 

separate dedicated 2-hour shaft. 

Only three of the elevators are assumed to be available for evacuation purposes. 

The fourth elevator is dedicated for use by the fire department. 

In addition to the elevator evacuation, a single stair leads down through the tower and 

discharges to grade. This stair enclosure is pressurized, and remains independent of the 

base building. The stair enclosure has periodic enlarged landings, which will allow 

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occupants to stop and rest as the descend through the building. In addition, the three 

stairs in the pod of the building are enclosed in 2-hour construction and pressurized. 

Each of these stairs has areas of evacuation assistance, with communication capability to 

the central control room. 

OCCUPANT LOAD DETERMINATION 

With a building of this type, it is important to understand and control the occupant load. 

Three methods were used to determine occupant load. Once the three calculations were 

performed, the lowest occupant load calculated is used as the limiting factor for the 

building. These three methods are as follows: 

1. Building codes typically allow holding areas or areas of refuge for horizontal exits. 

Where those holding areas are used, the code requires a minimum of 3 square 

feet per person for holding area.. Therefore, one of the limiting factors for this 

building was the size of the areas of refuge. The areas of refuge were calculated 

at one person per 3 square feet to determine their maximum holding capacity. 

This provides a factor of safety for several reasons: 

a. The area of stairs leading to the areas of refuge was not included in the 

holding area. These stairs would significantly increase the number of 

people that can be safely accommodated within an area separated from the 

fire by 2-hour construction. 

b. The calculations assume that no occupants are leaving the building via 

elevator or stair. Instead, they assume that all occupants are contained 

within the areas of refuge. 

c. The evacuation scenario is to evacuate the floor of origin, the floor above, 

and the floor below. Therefore, only a portion of the building will be 

simultaneously evacuated. However, the occupant load of the entire 

building is limited by the size of the area of refuge. 

2. The second means of limiting the occupant load of the building was based on 

code calculations. The expected occupant load, based on Table 33-A of the 

Uniform Building Code, was calculated for each floor of the building. The load 

was then totaled for the entire building and this occupant load is used as a 

limiting factor for the number of people in the building. 

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3. The third limiting factor is the capacity of the elevators to evacuate the people. 

The speed of evacuation was based upon NIST studies which contain calculation 

methods for elevator evacuation. In this project, it was concluded that a 1-hour 

time frame was a reasonable time to fully evacuate the areas of refuge. This 1- 

hour time frame was based on three of the four elevators being used for 

evacuation, with the fourth dedicated solely to fire department use. The 1-hour 

calculation also ignores the availability of the stair leading down through the shaft. 

Therefore, by this calculation, all occupants are expected to leave via the three 

elevators. NOTE: Operational considerations require the occupant load to be 

further limited if one of the elevators is down for repair. 

Once these three methods of calculations were completed, an occupant load of 

approximately 2,600 people was developed as the expected load of the building. This was 

the load factor around which the remainder of the building was designed. In order to be 

confjdent that this load factor is not exceeded, the building owner has instituted an 

occupant counting system which keeps track of the number of people entering and 

leaving the tower. Therefore, the load of the building will not exceed the calculated 

occupant loads. 

OTHER FEATURES 

The evacuation system for this building cannot stand alone. The fire protection features 

for this building were specifically designed to rapidly detect and suppress a fire, and 

control smoke generated by the fire. Some of the other features provided within the 

building are as follows: 

Automatic Sprinklers - The building is completely protected with automatic sprinklers. 

Sprinkler densities exceed those required by the codes. The sprinkler system was 

calculated to provide a very high density for the first four sprinklers operating, plus 

ordinary hazard density for the most remote 1,500 square feet. 

Water supply is from two pumps at street level which pump up to the pod. There is onsite water storage within the pod and two additional pumps sized for sprinkler plus 

standpipe demand in the pod. With these pumps and on-site water storage, redundant 

water supply is available. 

Detection and Alarm - The building is fully protected with automatic smoke detectors, 

except that kitchens contain heat detection. The smoke detectors are on an addressable 

system, with alarm verification to reduce the number of unwanted alarms. Manual pull 

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stations are also provided in the facility. In order to reduce unwanted pull station 

alarms, the manual pulls have been placed within the stahways. 

The alarms report to the main central control room for the Stratosphere Casino, as well 

as two auxiliaxy control rooms. One of the auxiliaq control rooms is located at the base 

of the tower, and the second is located within the area of refuge at elevation 750 feet. 

The control room within the area of refuge is accessed directly from the fire fighters 

elevator. Communication and infomation flow from the three control rooms is identical. 

The fire alarrn system is a Class A system, with separate risers running up through the 

shaft. The risers are separated by 2-hour construction. 

Ernereencv Power - Emergency power is sized to accommodate all portions of the fie 

protection system. This includes the fire pumps, fire alarm system, all elevators, smoke 

control and necessary lighting. The emergency power riser is routed through a separate 

2-hour shaft up through the tower in order to prevent a single event from impacting the 

primary and emergency power. 

Smoke Control - The building is provided with an automatic smoke control system. 

Upon actuation of an alarm, the floor or origin and any floors open to it go to full 

exhaust while adjoining floors are pressurized. In addition, the elevator lobbies for all 

floors are pressurized, as is the stair leading down through the shaft of the tower. 

Exhaust from the smoke control system is ducted to discharge above the ride level at the 

top of the tower in order to eliminate reintroduction of smoke into the building. 

CONCLUSION 

The Stratosphere Tower provided an opportunity and a need to develop a fire protection 

approach which departs from the typical building code approach to a building. Use of 

stairs as the sole evacuation method was not feasible or reasonable. Requiring all of the 

occupants to utilize stairs would result in an unsafe condition for many of the expected 

occupants of this building. A more reasonable method was to provide an area where 

people could be staged until evacuated, and a reliable means to perform that evacuation. 

The approach, as briefly descnied in this paper, provides protection in accordance with 

the overall intent of the buiIding codes, while departing significantly from the detailed 

requirements of code. Therefore, this is a true application of performance based 

approaches to fire protection in a building. 

JRQ:dp 

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FIGURE 1 

STEUTOSPH 
e- YOU ARE HERE 

FIGURE 2 

STRATOSPHERE TOWER n 
FIGURE 3 

STRATOW- CORPORATION