MGM+Grand+Hotel,+Las+Vegas+(1980)+-+(AE+537+Wiacek)

MGM Grand Fire - Las Vegas, Nevada (November 21, 1980) Christopher J. Wiacek, Integrated BAE/MAE, The Pennsylvania State University, 2010

toc

==

= Introduction = On the evening of November 21, 1980 a fire at the MGM Grand Hotel in Las Vegas, Nevada was started by "heat from an electrical ground-fault within a combustible concealed space in a waitresses serving station." (NFPA, 1982). Eighty-five people were killed in the fire and nearly 700 were injured fro m fire and smoke, making it the third highest fatality count hotel fire in the US (NFPA, 2008).

= Key Words = Hotel fire, electrical fire, smoke dampers, transmission of smoke through seismic joints and vertical penetrations

= Design and Construction =

The MGM Grand Hotel was a 23 story hotel and casino facility located at the intersection of East Flamingo Road and Las Vegas Boulevard, currently in use as Bally's Casino. The hotel consisted of 21 stories of guest rooms situated above two non-hotel stories- a double main level and casino and an interstitial space used for gaming floor security. The floors were numbered with an alternative numbering system used by the MGM Grand owners, depicted in Fig.1. Immediately adjacent to the casino and performance areas on the first floor to the east were a series of restaurants, clustered in the central portion of the building.

Construction on the building broke ground during 1972 and it was ultimately opened to the public in December of 1973. The building consisted of different construction types of varying efficacy with respect to fire protection. The hotel floors were resistant to fire and utilized a steel framing members which were protected by gypsum wall board (GWB) and reinforced concrete. Partitions were constructed from steel studs and GWB. The casino and interstitial levels were more sparsely protected; in some instances partitions did not fully extend above ceilings, an intention by the HVAC designer (NFPA, 1982).

= Events Leading Up to the Fire =

At approximately 7:00 AM on November 21, an employee of The Deli restaurant (Plan in Fig. 2) first noticed a small fire in the kitchen area while arriving to work. This employee notified hotel security, who in turn notified the fire department. Security began to evacuate the casino floor shortly thereafter, with eyewitnesses also reporting a rapid appearance of smoke. Several guests were trained firefighters and assisted in the evacuation process; they noted that the fire began to superheat the area and penetrate the upper ceiling approximately three to four minutes after evacuation began (NFPA, 1982).

= Fire Origin =

Based on investigations by the Clark County Fire Department (CCFD) and the National Fire Protection Agency (NFPA), several likely causes were identified for the MGM Grand Hotel fire. On the most superficial level, the most likely source of the fire was:

“Heat produced in the west wall partition of The Deli serving station as a result of electoral short-circuiting (a ground-fault) of an ungrounded electrical circuit conductor to a flexible metal conduit… The wiring was an extension of original wiring in the serving station and provided power to the refrigerator compressor unit and evaporator fan of a pie case located on the north wall of the station.“ (NFPA, 1982).

This condition was caused by three prime factors- improper grounding, improper installation, and galvanic action.

==Ground Fault == Further investigation by the NFPA and CCFD revealed that no dedicated equipment grounding conductor was found within the flexible conduit; therefore, it is assumed that all grounding was intended to be handled by the flexible metal conduit, electrical metal tubing, and receptacle box. Any discontinuity in this chain would lead to a scenario in which arcing currents would be possible. In one instance, it was noted that the aluminum flexible metal conduit itself was not properly connected to a receptacle box, and in turn the entire system was not properly grounded as shown in Detail B of Figure 3. (NFPA, 1982).

Galvanic Action
An investigation in greater detail by the Clark County Fire department documented that within the pie case near the compressor, portions of the aluminum flexible metal conduit came into contact with copper piping carrying refrigerant to the compressor shown in Figure 3. The vibration of the compressor allowed for increased contact between the two metals and facilitated a process known as galvanic action or galvanic corrosion between the two materials.

During this process, a small current is generated between the two materials and over time one metal will typically corrode at a faster rate than the other. Based on the Fourteenth edition of the Fire Protection Handbook (NFPA), “Aluminum carries a potential of + 1.7 volts while Copper carries -.34 volts,” signifying that the aluminum would corrode much sooner than the copper. This would create two potentially dangerous scenarios: a break in the grounding path, and the exposure of electrical conductors within the conduit (CCFD).

Improper Installation
<span style="font-family: Arial,Helvetica,sans-serif;">When installing conductors in a conduit, it is common to pull them through the length of the conduit. Any excessive abrasion due to irregularities in the interior surface of the conduit (more likely along the segments of the flexible conduit) would lead to the abrasion and eventual degradation of conductor insulation. Over time, temperature cycling of the conductor, conduit, and insulation could lead to portions along the wire where the insulation of the wire is worn away and the conductor could potentially transfer current to the conduit itself (CCFD). <span style="font-family: Arial,Helvetica,sans-serif;">The additional wire powering the pie case was also improperly installed, and gaps in the flexible conduit existed in the ceiling plenum and in the wall as shown in Fig. 3 Details A and B.

<span style="font-family: Arial,Helvetica,sans-serif;">Ignition
<span style="font-family: Arial,Helvetica,sans-serif;">When the three causes above were acting in unison, a dangerous combination was present. The galvanic action near the floor at the compressor corroded the flexible metal conduit over time. Heat from the compressor consistently pre-heated the conductor insulation, providing a lower required temperature from the conductor to wear away the insulation. It is then highly likely that uninsulated sections of wire formed over time, and the conductor came into contact with the flexible metal conduit. This contact energized the flexible metal conduit, and arc currents were then able to be formed across the disconnected portion of conduit from the improperly installed pie case wiring (CCFD, 1981).

<span style="font-family: Arial,Helvetica,sans-serif;">According to the Clark County Fire Department investigation, the construction materials chosen in this location gradually emit more and more flammable gases as they age. After approximately six years, enough flammable gases were present in the area to allow the arc current to ignite. Fuel sources were then readily available in the kitchen and restaurant spaces, and the fire was subsequently able to propagate at a rapid pace.

<span style="font-family: Arial,Helvetica,sans-serif;">Propagation
<span style="font-family: Arial,Helvetica,sans-serif;">The fire began to spread throughout the ceiling plenum via conductive and convective heat transfer. Once the fire spread above the restaurant seating area, the ceiling plenum had become hot enough to ignite the furniture in the space via radiation (CCFD).

<span style="font-family: Arial,Helvetica,sans-serif;">The lack of consistent slab to slab, full-height partitions allowed the flames to have a ready supply of air and a quick path out to the casino floor. Similarly, this allowed a free path for smoke to travel throughout the casino and interstitial levels. Smoke was able to penetrate seismic joints and unsealed areas in supposedly smoke-proof fire stairwells. Improper material selection on the smoke-proof stairwells allowed fire to burn through the walls in a relatively short amount of time, ultimately providing another direct path for smoke and fire (NFPA, 1982).

= Egress and Aftermath =

<span style="font-family: Arial,Helvetica,sans-serif;">Casino guests were evacuated almost immediately after flames were spotted in the Deli. According to several staff on duty, a fire alarm was said to have been activated but no such alarm was heard by other staff members or guests in other regions of the hotel.

<span style="font-family: Arial,Helvetica,sans-serif;">The main egress paths are depicted in Fig. 4; all but stairway E2 provided direct access to the exterior of the building (NFPA, 1982). Stairways at the end of each corridor were considered smoke-proof with respect to their construction- in addition, all of these doors locked from the inside after they closed to prevent access to other floors from the stairwell for security purposes.

<span style="font-family: Arial,Helvetica,sans-serif;">In total, 85 people were killed during the fire from smoke and carbon monoxide inhalation or other fire-related causes. The overwhelming majority of these fatalities were in the guest rooms or in circulation areas that were close to the unsealed seismic joints at the core of the building where smoke transmission would have been the worst, shown in Fig. 4. The lack of widespread fire alarm usage throughout the hotel can most likely attribute to the deaths that occured in rooms farther away from the central core. (NFPA, 1982).

= Repercussions and Lessons Learned =

At the time, the MGM Grand Hotel fire was one of the most costly in history- an estimated $30 million to $50 million of damage was a result of the fire. An additional $223 million in legal settlements was was also disbursed in the years after (NFPA, 2008). The MGM Grand Hotel fire is a prime example of how given the right conditions, several seemingly small and unrelated failures can occur in unison and together produce a disastrous result.

<span style="font-family: Arial,Helvetica,sans-serif;">Several important lessons were learned as a result of the MGM Grand Hotel fire. When the casino was being built, the owners had the opportunity to purchase a sprinkler system for the entire building at an increased cost compared to the partially sprinkled design that they had initially planned for. This system was viewed as too expensive by the owner- despite the

insistance of the fire marshal, Clark County code officials ultimately agreed with the hotel that it was unnecessary (NFPA, 1982). Many iterations of fire protection codes have since been enacted that require the entire building to have adequate fire suppression systems as a result of the MGM Grand fire..

<span style="font-family: Arial,Helvetica,sans-serif;">Several other design codes were also enacted as a result of this fire as well. All emergency feeders are now required to be 2-hour fire rated or utilize mineral insulated cable (Milne, 1998). This would prevent the preheating phenomenon and also provide increased resistance to abrasion during the construction process.

<span style="font-family: Arial,Helvetica,sans-serif;">Furthermore, In most cases partitions are now required to extend fully from slab to slab (or form zones, at the very minimum) in hotel spaces. This will contain the dispersion of smoke within a floor and prevent its propagation between floors. Circulation areas must be sealed properly and be constructed of very specific materials. Oftentimes pressurization tests are required in egress paths such as emergency stairwells to ensure that smoke cannot penetrate the space for a designated amount of time.

= Bibliography =

<span style="font-family: Arial,Helvetica,sans-serif;"> National Fire Protection Association (NFPA). "Preliminary Investigation of the MGM Grand Hotel Fire." 1980. Official investigation by NFPA regarding the MGM Grand Hotel fire.

National Fire Protection Association (NFPA). "Investigation Report on the MGM Grand Hotel Fire, Revised Edition." January 15, 1982. Official investigation by NFPA regarding the MGM Grand Hotel fire, including imagery and construction details.

National Fire Protection Association (NFPA). "Strategies for Creating Evacuation Messages." []> (September 28, 2010). Discussion to reaction to fire of hotel occupants and subsequent code changes.

Clark County Fire Department. "Official Findings of the Clark County Fire Department on the Fire that Occurred at the MGM Grand Hotel in Las Vegas, NV on November 21, 1980." 1980. Official investigation and correspondence of the Clark County Fire Department regarding the MGM Grand Hotel fire.

Hall, J. (October, 2006) "Structure Fires in Hotels and Motels." National Fire Protection Association (NFPA). Statistics regarding the magnitude of fatalities, cost, claims, and other criteria for hotel and motel fires.

National Fire Protection Association (NFPA). (January, 2008). "Summary of Fire Incidents 1934-2006 in Hotel Fires in the United States as Reported tot he NFPA, with Ten or more Fatalities." Statistics regarding the magnitude of fatalities in hotel fires in the US.

Touger, H.E. (March/ April 2001). "Investigation Report on the MGM Grand Hotel Fire, Revised Edition." January 15, 1982. NFPA Journal. <[]> (September 28, 2010). Best practices for hotel fire protection with specific references to changes affected by the MGM Grand Hotel fire.

Buerk, C.A., Batdorf, J.W., Cammack, K.V., Ravenholt, O. (January 8, 1982). "The MGM Grand Hotel Fire: Lessons Learned from a Major Disaster." Archive of Surgery. Commentary from a medical perspective on the impacts of the large MGM Grand Hotel fire on medical response, triage center configuration and communication, and emergency vehicle access.

Milne, L.J. (July/ August 1998). "Fire Protection of Critical Circuits- A Life and Property Preserver." IEEE Transactions on Industry Applications, Vol 34, No. 4. Brief sections detailing the impacts of the MGM Grand Hotel fire on electrical codes in hotels.

McGavin, G. "Nonstructural Design Philosophy." FEMA 454 Manual, Chapter 9. Impacts of structural design choices on fire protection systems.