Advocate staff photo by JOHN McCUSKER -- Surrounded by those who had lobbied for a smoking ban at city bars and casinos, Mayor Mitch Landrieu signed the ordinance into law Friday, January 30, 2015 at City Hall. Here he shares a pen with Dr. John Ochsner, Sr. Musicians union president Deacon John Moore is right.

Smoke ’em if you’ve got ’em, because the days of smoke-filled bars and casinos in New Orleans are now officially numbered.

Surrounded by public health advocates and City Council members, Mayor Mitch Landrieu signed the “Smoke-Free Air Act” into law in his office Friday.

“Many of these people around this table have been leading the effort for many years to raise awareness of the dangers of smoking,” Landrieu said.

The ban will go into effect on April 22, 90 days after it was passed by the City Council, officials said.

The smoking ban has been hailed by supporters as an important — if belated — step in protecting workers in the city’s service industry and performers from the effects of secondhand smoke. Pushed by Councilwoman LaToya Cantrell, it received the unanimous approval of the council last week.

Critics said it infringed on the freedom of bar owners and customers and could cause significant losses of revenue at many bars and Harrah’s New Orleans Casino, which must compete with establishments in nearby parishes that allow smoking.

Landrieu had held off on signing the measure until staffers could go through more than 100 last-minute amendments made by the council. Some members of the council, including President Stacy Head, also have suggested that further tweaks could be made before the ban goes into effect, though no one has put forward any specific proposals.

The measure includes exemptions for existing cigar bars and hookah bars and would allow “vaping” at existing e-cigarette retailers. Before the measure passed, council members backed off of restrictions that would have barred smoking in the patios or courtyards of bars or within 25 feet of businesses’ doorways.

The city’s Health Department is still working out the details of how the ban will be enforced, though Director Charlotte Parent said the widespread adoption of restrictions on smoking nationwide means the city “doesn’t have to re-create the wheel.”

Before the ban goes into effect, the department will begin a public education campaign to ensure bar owners and patrons are aware of the law, Parent said.

After that, the department likely will rely on complaints from residents to catch those violating the ban, she said. The exact details of whom people would call with complaints and how those complaints will be handled are still under discussion.

Based on the experience of other cities, Parent said, she expects New Orleans will not have to deal with many violations after the ban has been in place for a short time.

“What we’ve seen multiple times is that we see complaints in the beginning but a dramatic decrease” as people begin voluntarily complying with the policy, she said.

Follow Jeff Adelson on Twitter, @jadelson.