The Nevada Clean Indoor Air Act, which took effect in 2007, bans smoking in any indoor space where minors may be present and where food is served. The new bill, which now moves to the Assembly for consideration, would allow taverns that offer food to permit smoking if they bar people under 21 from entry.

Many taverns in Nevada have video poker slot machines that provide a significant source of revenue, but the Nevada Tavern Owners Association said gambling revenue had fallen considerably since they had to stop patrons from smoking. Smokers have decided to gamble at the local casinos instead because the law excluded casino floors from the ban, said Geno Hill, the association president. “Our members’ gaming revenues are off 20 to 30 percent since the ban, and that’s before the recession,” said Mr. Hill, owner of the Rum Runner taverns in Las Vegas.

Gambling revenues over all have plummeted in Nevada over the past year, down 18.1 percent in February versus February 2008, according to the Nevada Gaming Control Board.

While a few cities, including Champaign and Urbana, Ill., and Friendship Heights, Md., have repealed smoking bans over the past decade, antismoking advocates said they knew of no statewide restrictions that had been eased or undone.

The City Council in Atlantic City voted last year to ban smoking in casinos, but it suspended the ban for a year after casinos said business had dropped 10 to 20 percent under it. The New Jersey Legislature is now considering making a ban on smoking in casinos a state law.

Health advocates dismiss the idea of a link between lost business and smoking bans, insisting that people get used to the prohibitions over time. Twenty-three states ban smoking indoors at bars and restaurants.

Jennifer Stoll-Hadayia, public health program manager for the Washoe County Health District, which includes the Reno area, predicted that state legislators could face a backlash against the measure as it moved toward passage in the Assembly. More than 54 percent of Nevada voters supported the measure in 2006.

Senator John Lee, Democrat of Las Vegas, was one of five to oppose the new measure and said it was ironic that within hours of the Senate action, the Assembly passed a bill requiring public hospitals to provide outpatient cancer treatment to the indigent.

“One house says it’s O.K., if you’re over 21, to go ahead and kill yourself and everyone around you — ‘We think that’s great, it’s your freedom’ — but the other house says, ‘Wait a minute, my gosh, if they have cancer we’ve got to take care of them,’ ” said Mr. Lee, a cancer survivor. “People don’t seem to see the connection between the two.”