Downstairs in the casino, little remained of the MGM Grand Hotel’s former glory. In the early morning hours of 21 November 1980, a fire had broken out in the Las Vegas landmark, ripping through the lounge in an explosive wave that instantly killed everyone in the area. Bodies sat frozen in front of what had once been slot machines, now no more than blackened pillars jutting upward from a flow of melted slag along the floor. The room’s plastic and chrome-plated decor, it turned out, had been as much a facade as its promises of riches.

Fortunately, the Clark County Fire Department had responded immediately, and the blaze never spread beyond the first floor. From where David Demers and his fire investigation team stood on the 23rd floor, no one would have even felt the temperature rise. Why, then, were they surrounded by corpses?

When the MGM Grand Hotel and Casino first opened in 1973, it was the largest hotel in the world, with advertisements claiming more square footage than the Empire State Building. The first floor boasted a movie theater, two stages, and five restaurants, yet these were no more than satellites to the main attraction: a casino the size of three football fields. The hotel’s 26 floors stretched into the sky as a bold declaration of not only wealth, but vitality. Las Vegas had beaten back the desert, and its newest crown jewel seemed impossible to tarnish.

Unfortunately, when the fire struck seven years later, the MGM Grand would live up to its record-setting reputation. By the end of the day, 85 people would lose their lives and approximately 700 would be injured, including 14 firefighters who had to be hospitalized. It was the deadliest hotel fire in the nation since the introduction of modern fire safety codes in the 1940s.

Though not especially onerous, the codes at that time were complex and open to interpretation. One rule, for example, stated that sprinklers must be installed in all public areas, but another exempted areas expected to be occupied 24 hours a day, on the theory that someone would always be there to put out a fire. Smoke detectors were a given, but commercial builders could install them inside the ventilation system rather than in each individual room for efficiency’s sake—many builders preferred this option because it placed the detectors out of sight, where they could not detract from the aesthetics. Buildings underwent a relatively exhaustive list of safety checks to pass final inspection, but once open to the public, reassessment was minimal, no matter how many years had passed.

Regulations also varied state to state. Some, like Connecticut, had banned highly flammable building materials altogether. Others, like Nevada, operated on the philosophy that treatment was easier than prevention, and required only the emergency stairwells to be sealed with smoke-proof, fire-rated materials.

The builders of the MGM Grand in particular seemed eager to save money wherever possible. Construction had gone on longer than expected, and inspectors had given the hotel a failing grade multiple times as it neared completion. It was a contractor, in fact, who brought up the 24-hour exemption for sprinklers; only after they pointed it out to the fire marshal’s office did the fire marshal begrudgingly agree that most of the hotel did not legally require sprinklers after all.

Once the resort finally opened, however, it boomed. The opening weekend featured performers Cary Grant and Gregory Peck, among others, and Dean Martin’s famous Friar’s Club roasts took place there each year. On the weekend of the fire, all 2,000 guest rooms were sold out, packed with a typical array of traveling families and partying bachelorettes, touring performers and sightseeing retirees. Many had booked their rooms on relatively short notice, after the large computer industry trade show known as COMDEX changed locations to another venue at the last moment.

For the investigators who examined the hotel in the days following the tragedy, however, it was the distribution of bodies, rather than their number, that was most perplexing. Guest rooms began on the fifth floor, and the firefighters’ ladders had been able to reach windows as high as the ninth. Above that, the victims’ lives should have depended mostly on their wits and perhaps how much they’d had to drink the night before. Logic would suggest a distribution favoring the lowest and highest floors, close to escape points on the streets below and the roof above, with those in the unlucky middle being farthest from the exits.

Instead, only one person between the 5th and 18th floors had died. Above that, the death toll spiked dramatically, peaking with 14 bodies on the 23rd floor. Even on the top two floors, just steps from safety, no fewer than eight people had perished.

Overwhelmed by the magnitude and complexity of the situation, the Clark County Fire Department requested assistance from both the United States Fire Administration and the National Fire Protection Association, where David Demers was the manager of the Fire Investigation Division. Now it was their job to figure out exactly what had happened, from the moment the fire began all the way until the last victim died from complications almost a week later.

The fire’s origin, at least, was easy to identify: it had begun inside the wall of The Deli, a 24-hour casual eating area just beyond the main showroom. Sometime after the original construction of the hotel, a new refrigerated pastry display case had been installed, and the copper pipes of its compressor had been run through the same section of wall as the electrical conduit for the room. This was undoubtedly a bad idea, but not inherently destructive in itself.

The machine had been improperly secured, and vibrated slightly from the day it was installed. Over time, these vibrations caused the pipes to shift sideways until they touched the aluminum conduit, which had also been improperly installed with no ground wire. The copper ate away at the aluminum in a process known as galvanic corrosion—the same electrochemical process that allows batteries to work. Continued vibration then wore through the wire insulation. The entire process took several years, but the copper eventually came in direct contact with the electrified wires, heating the pipes “to the point of glowing metal,” according to the investigation team’s official report.

With minimal oxygen inside the wall, the fire smoldered and spread for an unknown period of time. The Barrymore restaurant next door was not a 24-hour facility, and had fate sent the flames in that direction, sprinklers would have quickly doused them with no serious harm done. Instead, the fire broke through into The Deli just before 7:00 a.m. Unfortunately, lacking business in recent years, The Deli had begun closing overnight. No one was there.

A hotel employee named Tim Connor happened to take a shortcut through the empty restaurant at 7:13 a.m. and was horrified to discover “a sheet of flames running from the top of the counter to the ceiling.” The fire report noted that from Connor’s vantage point, he could only have seen one corner of the much larger fire already in progress—but regardless of size, he couldn’t put it out. The Deli’s fire extinguisher was missing.

Connor called security from a phone on the wall, just before a wave of heat and smoke knocked him to the ground “like a sea in a wind tunnel.” He barely managed to scramble along the floor out of the restaurant.

The Barrymore had been properly equipped with both an extinguisher and a wall-mounted fire hose, but by the time Connor and other responding employees dragged them around to the source of the fire, it was too late. Flames had reached the ceiling tiles, which were attached with an especially flammable adhesive that even the Nevada building code had banned from commercial use three years earlier. The fire began to spread above the men’s heads much more rapidly, between 5 and 10 feet per second. Realizing they would soon be trapped, they fled back into the casino, slamming the thick double doors behind them and shouting a warning to everyone in their path. Less than six minutes had passed since Connor had discovered the fire.

The closed doors slowed the flames for a few critical moments in the foyer between the restaurants and the casino, but the added time came at a price. Fire traveling along a floor or other interior furnishings will generally spread in a predictable path from one item to the next, depending on the fuel available to consume—a table next to a couch does not burn until most of the couch is alight, for example. But fire in a ceiling or upper wall burns more thinly and evenly, due to the uniform surface, and usually the flames are not large enough to reach flammable items below. Instead, the room temperature steadily rises until a phenomenon known as “flashover” occurs, when all of the combustible material along the floor reaches its spontaneous ignition point at the same moment.

In the small but lavishly furnished foyer, the resulting explosion blew off the doors to the casino entirely, flooding the room with fresh oxygen and extending the fireball into the lounge. Here, too, the ceiling tiles had been attached with the same highly flammable adhesive, which experts estimate the fire consumed at 15 to 19 feet per second. Those who had not yet heard or obeyed the shouts for evacuation died instantly.

Fortunately, local firefighters reached the scene within just two minutes of the first call and valiantly fought back the flames to their source. Sprinklers in other sections of the hotel triggered, containing the fire to the areas already engulfed. Within less than an hour, the blaze was under control. For the guests still inside the hotel, however, the ordeal was far from over.

Contrary to building codes, the elevator doors had not been tightly sealed on any level of the hotel, sometimes leaving a gap as large as 3/4 of an inch. Waves of heat nearing 10,000º F (5,540º C) entered the elevator shafts near the casino. Within minutes, the stainless steel cables melted, plummeting the elevators past the inferno and into the basement. Had any of the five guests inside the elevators survived the fall, their luck didn’t gain them much; moments later, the counterweights—no longer attached to anything—also fell and crushed the cars beneath them.

One elevator did not fall, but its four occupants died from asphyxiation after it became stuck on the 20th floor. Normal operation would have required the elevator cars to open their doors and cease operation as soon as a fire alarm tripped in the building, but the unsightly smoke detectors supposedly “hidden” inside the ventilation system had never been installed at all. The main alarm could be activated from the security office, but neither of the two employees on duty did so before running to the aid of evacuating guests.

Most of those guests were still upstairs, unaware of the chaos going on below. Some died in their sleep because the fan coil units in the guest rooms ran continuously, pumping smoke in from the hallway. Designed to be vented into a vertical air shaft leading outside, the units in the MGM Grand had been connected to interior air sources for unknown reasons. Others woke to the sounds of shouts or the sirens on the street below, but found the halls already impassable.

Even those who made it to the exits were not yet in the clear. Of the six emergency stairwells, the supposedly fire-rated materials failed in four, and smoke flowed freely into them almost as soon as the fire began. In addition, all of the doors leading into the stairwells were set to automatically lock from the inside. With the ground floor inaccessible, many evacuees found themselves trapped, forced to flee upward as many as 20 flights of stairs in thick smoke before they reached the safety of the roof.

“Smoke entered the wall spaces indiscriminately,” according to Demers’ report, and the increasing pressure from below forced it through any available opening. Dark soot would later be found surrounding the shower heads and faucet fixtures in many of the bathrooms. One man, who was rescued from his smoke-filled room by firefighters after more than an hour, said he and his coworkers had thrown chairs through their hotel window to vent the room as best they could, and then lay on the floor “with our noses in the corners saying Hail Marys.”

Yet that hadn’t been everyone’s experience. Smoke poured into the hallways each time the stairwell doors opened, but otherwise their fireproofing failed only at the bottom levels. Thousands of guests between the fifth and 18th floors managed to navigate the halls until they reached one of the two good staircases. Investigators found minimal smoke damage on those floors—despite the floors suffering the same defects of elevator doors with gaps and unvented fan coils. The smoke on the uppermost floors had come from somewhere else. This anomaly finally led investigators to the most appalling failure in the hotel’s construction.

Commercial ventilation systems require “fire dampers” at regular intervals—a large metal panel held open by a piece known as a fusible link. The link has a low melting point, which breaks in the heat of a fire and slams the trap door shut to prevent smoke from circulating into the ventilation system. In the MGM Grand, all of the fire dampers on the lower levels had been improperly installed, and the ones over the casino in particular had been permanently bolted open by workers who either didn’t know their purpose or simply found them inconvenient. The links melted, but the dampers stayed open.