...a piece of machinery or suffocating in a confined space. Workers chime in with their own stories. We soon are all survivors as well as workers, reciting horrors of toppled materials, errant bucket swings, iron splinters. Is this how soldiers feel in combat?

Trapped in such an existential nightmare, one worker saw only randomness. “This is a crapshoot out here,” says Kim Murray, a local operating engineer and OSHA 10 instructor. “One guy might fall off a 12-ft ladder and live, while another might fall and die.”

Classmates bond fast, and first-day jitters dissolve. Attention spans grow short as time wears on, leading to restlessness, squirming in seats and doodling. These are physical guys that are used to being in constant motion; sitting still for long periods of time takes them out of their element, tiring them more than swinging a hammer all day. Instructors provide intermittent breaks, which everyone uses to smoke, snack or make cell-phone calls to girlfriends and wives. Others stretch out and rest their eyes.

When the training concludes, workers receive their OSHA 10 card, enabling them to obtain a jobsite badge that is checked and rechecked by security personnel entering and exiting CityCenter. Badgeless workers, as well as those without reflective safety vests, hardhats and protective eyewear, are refused site access.

Asleep at the Wheel

Fatigue is a constant challenge. Workers, per union contracts, are given 30-minute lunches and intermittent breaks. Many stretch, relax, rest and refresh during this time. One guy routinely flattened himself on a concrete slab, lit a cigarette and laid it atop his chest. He proceeded to pass out cold amid the noise and chaos, sleeping soundly. The cigarette was a timer: When it singed his fingers, the break was over.

Weariness can compromise safety. It can result in slow movement and feelings of heaviness, symptoms that produce psychological distress and impair thinking, according to a 2008 University of Texas study. Sluggishness or a lack of concentration can make the difference between life or death on a construction site.

Although the training does not address the issue, the OSHA 10 program wins at least one backer. “I think this is a damn good idea,” says Trent Vanoostendorp, a 20-year Las Vegas veteran plumber and pipefitter. “People take shortcuts, or they are trying to be heroes and rush work. It is your attitude that makes you safe.”

By the third day, actual work begins. I meet Mike Janowski, a Chicago-native Perini superintendent, who takes me atop CityCenter’s highest point—the 600-ft-tall “Aria” hotel tower. An aria, in opera, is an elaborate vocal solo, but nothing here is done alone. Workers rely on one another. We travel along the building’s outer edge inside a red metal-mesh cage on a construction elevator that feels like a low-impact carnival thrill ride that creaks and groans as it moves. It is crowded, with everyone pressed against one another. Riders enter and exit at different floors, carting tools and building supplies. Union stickers and duct-taped photocopies festoon the cage interior: One sheet announces a picnic, another sells a “slightly used power saw—cheap!”

We exit at one of the mammoth 125,000-sq-ft floor plates that engulf workers in darkness, as a fine layer of dust coats the interior like a soft, silent snow. Stale air and ventilation are major dilemmas due to constant sawing, grinding and vehicle exhaust. Airplane-sized propeller-blade fans help circulation, but it is not enough. Workers use comfort masks, respirators and water for improved breathing. Aria has 1,700 construction workers, CityCenter’s highest concentration, but Janowski knows everyone’s name and navigates the terrain efficiently.

“Plans were only 30% complete when we began construction,” says Janowski, a Chicago Bears football fan, who cannot count how many times plans changed. Yet the project remains largely on schedule to finish in December. Perini is acutely aware of what is riding on CityCenter: It is a showcase project for a publicly traded company. “I think about it all the time,” admits Richard Rizzo, Perini’s vice chairman. “It keeps me awake at night.”

Leaders should be concerned because it is not clear that 10 hours of safety training can stem the carnage. If it were that simple, no one would ever get hurt. That seems unlikely because the classroom instruction, booklets and blunt warnings do not tell the whole story. Perini may have eliminated the mixed message that “safety is first but productivity is even more important.” But you cannot force someone to behave safely even if you teach them all the rules. You cannot badger or terrify.

I cannot say for sure why the fatalities stopped at CityCenter. Maybe tragedy helped forge a familial closeness, a protective atmosphere with more caring and guardianship. Maybe craft workers are being more cautious amid a deepening recession in which high-paying jobs are in short supply. But even that does not stop you from getting tired—and tripping and falling.