No gambling allowed on smoke control in Las Vegas
Clark County, Nev., has required smoke control systems since the disastrous 1980 MGM Grand fire, which killed 87 people, and the 1981 Hilton Hotel fire, which killed eight people. Three-quarters of the fatalities in these Las Vegas fires were due to smoke inhalation that occurred far from the fire areas. Large quantities of toxic smoke traveled to upper hotel floors through elevator shafts, building seismic joints, ventilating shafts, utility shafts, and stairwells.
The Las Vegas Retrofit Ordinance of 1981, which covers both smoke control and sprinklers, was enacted in response to these fires. Eleven of the 19 major features of the Retrofit Ordinance limit the production and spread of smoke in large buildings built after 1980. Because smoke control is difficult to retrofit into existing buildings, it only is required for hotels and casinos. Sprinkler systems were retrofitted within four years in the 38,000 hotel rooms existing at the time of these two fires.
Codes and standards
There are more than 137,000 hotel rooms in Las Vegas. More than 10,000 hotel rooms will be added to the standing inventory in 2008, and many large hotel/casinos are under construction or in the design stage. The 2007 permit valuation for Clark County, which includes Las Vegas and the Las Vegas strip, was a record $8 billion, and a number of current projects have multi-billion dollar budgets (see “Billion dollar babies,” page 26).
Smoke control systems typically are required along the Las Vegas Strip for high-rise hotel, condominium, or time-share towers taller than 55 ft; malls; atriums; arenas; underground buildings; and enclosed parking garages (see Figure 2). Smoke control systems also are required for low-rise buildings attached to high-rise buildings, unless there is a 3-hour fire- and smoke-rated separation between the buildings. Off-Strip buildings that require smoke control include office towers, hospitals, medical centers, institutional centers, and correctional facilities.
Las Vegas smoke control systems must pass the rigorous design evaluation and testing procedures of the Building Division of the Clark County Dept. of Development Services. One challenge is posed by the shear number of requirements and specifications. There are 39 sections in the 2006 International Building Code (IBC) and an additional five sections in the 2006 Uniform Mechanical Code that impact smoke control systems. Many provisions are derived from NFPA Standard 92A, “Smoke Control Systems Utilizing Barriers and Pressure Differences.”
The Clark County process
The Clark County Dept. of Development Services usually becomes aware of the design features of a hotel/casino at a pre-submittal meeting, which is required for all major projects. The actual project design may have been under development for many months by the date of the pre-submittal meeting. The smoke control design features are listed in a document called the Fire Protection Report, and may be further clarified in mechanical, architectural, and fire alarm drawings.
The smoke control system often uses a combination of methods described in Section 909 of the IBC, including the passive method, the exhaust method, and the pressurization method. Systems using the exhaust method are designed to the provisions of NFPA Standard 92B, “Smoke Management Systems in Malls, Atria and Large Spaces.” Use of performance-based codes allows the designer to submit an alternate approach for consideration.
The Fire Protection Report typically is submitted with the architectural permit application and is reviewed and approved by the Building Plans Examination staff, usually licensed fire protection engineers for major projects. The Fire Protection Report also must be reviewed and approved by the Clark County Fire Dept., which is responsible for acceptance of the fire detection and alarm systems, emergency notification system, fire sprinkler system, any alternative automatic fire extinguishing system, standpipe system, and elevator emergency response system. Tenant improvements may be reviewed by an architectural plans examiner.
An approved Fire Protection Report establishes the design philosophy for the building smoke control system. A major project may resubmit the report for review several times prior to approval. The most important document in the Fire Protection Report for the personnel installing the smoke control system in the field is the smoke control matrix, which usually is provided as an appendix. This matrix typically lists the initiating devices for smoke control in a column at the left side of the document and shows the functional response of the smoke control system in a row at the top.
If the Fire Protection Report notes that a smoke control system is required, then the reviewer notes this requirement on the permit and a special inspection agreement for smoke control is issued with the permit. The owner must then hire a qualified inspection/testing agency to witness the proper operation of the system.
Once a mechanical permit is issued for a building, the Building Division staff places a hold on scheduling of rough mechanical inspections. The hold is placed for review and approval of smoke control diagrams. The diagrams combine design details of the smoke control system, which previously may have been scattered among the mechanical, fire alarm, architectural, and possibly electrical drawings. The hold on scheduling of rough mechanical inspections ensures that ductwork and dampers are not enclosed prior to inspection of this important smoke control equipment.
Smoke control diagrams are submitted for review by Building Division engineers. The diagrams include:
Control wiring details
Plan views showing smoke and sprinkler zone boundaries
Riser diagrams showing duct and smoke control equipment in elevation views
Layout and location of major smoke control equipment
Detailed smoke control matrix
Smoke control equipment (see Figure 1) typically included in the diagrams are:
Dampers and doors
Area, heat or duct detectors
Sprinkler water-flow switches and other initiating devices.
The detailed smoke control matrix expands on the conceptual matrix in the approved Fire Protection Report. It lists every initiating device in the system and the functional response of the smoke control equipment to that initiating device (dampers and doors open or close, fans start or stop, etc.). The mechanical designer usually generates smoke control diagrams.
The smoke control diagrams are reviewed carefully, because they serve as the basis for drafting test scenarios and programming and accepting the smoke control system. Approval of the smoke control diagrams is the first inspection specifically accepted. The system can now be inspected in the field using approved drawings.
As the general contractor continues with building construction, floors, walls, ceilings, shafts, chutes, stairs, doors, and other smoke zone boundaries are completed (see Figure 4). The mechanical subcontractor installs ducts, dampers, fans, pressure relief hoods, the sprinkler system, and the various initiating devices for the smoke control system.
Rough mechanical inspections are scheduled and completed upon installation of mechanical equipment in different sections of the building. Some sections of the building are unique; others are repetitious, such as the middle section of the hotel for many floors. Those unique or nearly so are:
Restaurant and retail areas
Back-of-house support areas
First few floors of the high-rise hotel
Top floors of the high-rise hotel.
The first few floors of the high-rise hotel often are called the podium. The top floors often feature much larger rooms than the middle levels, sometimes having two-story penthouse suites.
Inspections and testing
While the building is under construction, the building inspectors of the Clark County Building Division inspect construction of smoke barriers and placement of smoke control equipment. The special inspection agency assigns inspectors who attend site meetings on the smoke control system and perform acceptance testing on the smoke control equipment. The testing agency fills out a daily report any time they are on site. These reports and any test results are maintained on-site at the general contractor’s office for review by the Building Division.
The first acceptance test usually is performed by a test and balance firm that ensures the riser duct, which connects all the floors for smoke exhaust, is pressure tested in segments that are typically 15%%MDASSML%%20 stories high. The pressurized duct must hold 150% of the design pressure with a maximum leakage of 5% of the design airflow. The building inspectors ensure that wall, floor, and ceiling constructions are tight, with joints and utility penetrations properly sealed, and any openings are protected by fire- and smoke-rated doors, dampers, or curtains.
Acceptance testing of the smoke control system begins in earnest as the building nears completion and the smoke control graphics panel (see Figure 3) is installed in the fire command center, a special room at ground level that serves as the emergency response location for the fire department. The general contractor and mechanical subcontractor test the smoke control system after the panel is energized. A system programmer will staff the fire command center during the weeks required to shake down this complicated system until the graphics panel is free of trouble lights.
The smoke control agency writes proposed test scenarios from the matrix on the smoke control diagrams and submits these as a test plan to the Building Division. The test plan also must include the percentage of passive smoke zones that must be leaktested with door fans, or door fan assemblies, in building areas where the passive method of smoke control is used.
The general contractor notifies the testing agency when the smoke control system is ready for acceptance testing. The testing agency then tests all initiating devices, verifying the proper responses were obtained. Pressure readings will verify that the required minimum 0.05-in. water gauge differentials have been obtained. Door-opening forces are measured to ensure they are less than 30 lb. Exhaust quantities, leakage rates, or airflow quantities are measured, if required. The testing agency then writes a Non-Conformance Report for any condition that is not acceptable.
After the system has been tested successfully to the test plan, a final inspection report is submitted to the Building Division for review and approval. Approval of the final report is the second of two building inspections accepted specifically for the smoke control system (smoke control diagram approval is the first). After the final report is reviewed and approved, the contractor schedules a final mechanical and building inspection. During this inspection, Building Division inspectors ride atop an elevator cage to check elevator shafts for any unsealed joints or utility penetrations. They also perform room walks inspecting each of the thousands of hotel rooms in a single new hotel.
Following approval of these inspections, the contractor schedules the fire department and building division for a life-safety systems test, which is an integrated acceptance test of all the life-safety systems. A life-safety systems meeting, called a pre-TCO (Temporary Certificate of Occupation) meeting, often is scheduled prior to the system test, with the general contractor, appropriate subcontractors, fire department, building division, and testing agencies in attendance. The system test is performed to the scenarios in the test plan and some of the tests will be conducted with systems on emergency generator power.
Occupancy and partial occupancy
Upon successful completion of the life-safety systems test, the general contractor will apply for a Certificate of Occupation for the building. If the building is not complete, a TCO may be granted. All life-safety systems must be complete in the building section to be occupied.
If an owner wants to occupy a middle portion of a building while construction continues on lower and upper floors, two buffer floors are required below the occupied floors and one buffer floor above the occupied floors. These measures protect occupants from adjoining construction activities. More floors are required below because hot smoke is naturally buoyant. All life-safety systems must be complete on the buffer floors. However, they will not be occupied because their purpose is to provide some vertical separation between occupied areas and areas still under construction. As an example, floors 8 to 26 of a 30-story hotel would have to be completed to allow floors 10-25 to be occupied.
|Arnold has extensive megaproject experience and has inspected smoke control systems on the Las Vegas Strip for 12 years.|
Smoke control methods
In modern Las Vegas high-rise hotels, condominiums, and time-shares, a “pressure sandwich” is used to contain and exhaust smoke from floors where there is a fire. A pressure sandwich is achieved with a combination of tightly sealed floor and wall construction and by exhausting the fire floor. A pressure differential of 0.05-in. water gauge between the fire floor and adjacent floors or smoke zones is sufficient to ensure no smoke leakage occurs from the fire area. The fire floor is under negative pressure from being exhausted, and the adjacent smoke-control zones are positively pressurized.
Additional smoke control concepts that are codified in the International Building Code and used in modern high-rise Las Vegas hotels include the following provisions:
Positive pressurization of stairwells and elevator machine rooms to prevent smoke intrusion into these areas
Exhaust of smoke from the fire area to maintain a smoke-free layer for some distance above the floor (usually 10 ft) to allow personnel a safe exit path and also allow emergency responders a safe access path
Confinement of smoke to a single smoke zone using smoke-tight barrier construction and closure of openings in smoke barriers
Shutdown of normal ventilation equipment to deny oxygen to a fire and restrict smoke dispersion
Exhaust of hotel corridors (initiated by corridor smoke detectors) to prevent smoke introduction into neighboring guestrooms
The use of vestibules to maintain stair pressurization and corridor exhaust in high-rise hotels while minimizing door opening forces
Shutdown of re-circulating fans if smoke is detected in their associated ducts to prevent the spread of smoke beyond the zone of origin
Early activation of smoke control to prevent flashover or backdraft conditions
Separation of exhaust outlets and fan inlets to prevent the re-introduction back into the building of exhausted smoke.
Billion dollar babies
Mega-resorts under construction along the Las Vegas Strip include:
$ CityCenter ($9.2 billion),
$ Echelon Place ($5 billion)
$ Cosmopolitan ($4 billion)
$ Fontainebleau ($3 billion)
$ Encore ($2 billion)
Clark County resources online
To assist fire protection engineers, Clark County has published the “Fire Protection Report Building Design Guide,” which provides information on how to address the smoke control system in the Fire Protection Report. The guide is available on the Clark County Web site at
Also online are:
• A list of qualified smoke control testing agencies. Navigate to the Department of Development Services, click on Building Services, click on Engineering under Services, click on Approved Listings under Services, and then click on Quality Assurance Agencies, Smoke Control and/or Test and Balance.
• A checklist that describes what information needs to be on smoke control diagrams. It is Attachment A to Technical Guideline TG-60 (Smoke Control). TG-60 can be found by navigating to the Department of Development Services. Then, click on Building Services, click on Engineering under Services, click on Technical Guidelines under General Info, and finally, click on TG-6-2006/IBC.
• A checklist describing the information required in the final test report. The checklist for final reports is Attachment B to TG-60.
Unlucky numbers can floor designers
Of course, the number 13 is generally considered an unlucky number in Las Vegas and is rarely used on a floor numbering system. In addition, the number 4 is generally considered an unlucky number and is often deleted from the floor numbering system, which results in the confusing situation where some 30-story hotels have penthouse suites located on floors numbered in the 50s.
Unique smoke control in Vegas
The booming Las Vegas resort construction scene has unique aspects that affect smoke control systems. Many resorts have very large indoor arenas for concerts and sporting events. These arenas generally use either the exhaust method (verify a design exhaust quantity is achieved) or modified airflow method (measure airflow at perimeter openings) for smoke control. The system typically is activated by sprinkler water-flow switches.
An integral fixture of the Las Vegas resort scene also is the showroom that houses spectacular stage sets and plush multi-level seating areas similar to opera houses. The extravagant finish materials in the seating areas are protected by layers of fire detection systems, including smoke detectors, infra-red detectors, spark/ember detectors, optical detectors, air-sampling systems, and beam detectors. Additional protection for the seating and show areas is provided by deluge systems and water cannons. Smoke control systems for seating and show areas may operate in different modes using either the exhaust method or the pressurization method, depending on the position of the proscenium curtain. To prevent inadvertent operation of the deluge system, three detection systems often are installed, two of which must alarm before the deluge system is activated.
Many Las Vegas hotel properties have extensive convention areas, exhibit halls, and ballrooms. High-ceiling convention areas and exhibit halls typically use the exhaust method for smoke control while ballrooms use the pressurization method, all usually activated by sprinkler water-flow switches.
Also, many new resorts are complemented by extensive retail malls on the property. Individual stores are clustered into tenant smoke zones, with 10 to 20 stores in one tenant zone, and the mall area is divided into different mall smoke zones. A mall may be as long as a mile and occupy several levels. Because mall areas typically have expansive ceilings, an individual mall zone can be a very large space. The passive, pressurization, exhaust, and modified airflow methods have all been used in shopping malls.