The answer is no, currently there are no totally non-smoking casinos in Las Vegas. It has been tried in the past, but the subsequent loss of revenues proved prohibitive. It's not uncommon for a casino's poker room to be smoke-free. Bally's, Bellagio, Binion's, Circus Circus, Excalibur, Golden Nugget, Harrah's, Imperial Palace, Jokers Wild, Luxor, Mandalay Bay, MGM Grand, Mirage, Monte Carlo, Orleans, Palace Station except between midnight and 8 am, Aladdin, Plaza, Poker Palace, Rio, Riviera, Sahara, Santa Fe Station, Stardust, Stratosphere, Sunset Station, Texas Station, Tropicana, and Wynn all have non-smoking poker rooms, while Boulder Station and Cannery each have non-smoking tables in their poker rooms. However, the actual casino floor is another story entirely.
Many casinos (Green Valley Ranch, Harrah's, Hilton, Mandalay Bay, MGM Grand, NY-NY, Palace Station, and Rio among them) offer non-smoking table games on request, meaning that someone has to request it and everyone else at the table must agree before the table is so designated. Many others (including Bellagio, Buffalo Bill's, Excalibur, Gold Coast, Imperial Palace, Luxor, Mirage, Orleans, Palms, Plaza, Primm Valley, Rampart, and Rio) have designated non-smoking tables, though they tend to move around frequently and are subject to the discretion of the shift manager. Two casinos have designated non-smoking pits: Hard Rock with blackjack and pai gow, and Santa Fe Station with blackjack, pai gow, and roulette (open 11 am to around midnight).
As for non-smoking slot areas, the information is even more sketchy. Bellagio, Boulder Station, Excalibur, Fiesta Rancho, Gold Coast, Green Valley Ranch, Harrah's, Sam's Town, Santa Fe Station, and Texas Station all claim to have small sections of slot machines that are smokeless. However, considering the close proximity of slot machines to one another, it seems that these small areas would do little to shield patrons from the smoke of the smoking areas -- much as the former "smoking section" at the back of aircraft effectively rendered about half the plane a smoke zone. Click here for our survey of non-smoking areas around town.
To conclude, we suggest that anyone with a serious smoke aversion should call ahead to the casino and ask to speak to the slot office, the players club, or the pit, depending on which games they intend to play. Hopefully, that way you will receive up-to-date accurate information regarding non-smoking areas on the day of your visit.