Albuterol inhalers are for emergencies, for quick relief of wheezing. Patients also need daily medication to control their asthma and prevent flare-ups. Someone who's using the albuterol inhaler more than a few times a month isn't well-controlled, and his or her doctor needs to determine why, stresses Dr. Paul Greenberger of Northwestern University, president-elect of the American Academy of Allergy, Asthma & Immunology.

Here's the rub: Recent research suggests only one in five children has their asthma under good control; no one knows how many adults do.

The last to go CFC-free will be the poor and uninsured whose asthma is less likely to be controlled, says Leo, who researches that issue at Michigan's Center for Managing Chronic Disease.

Albuterol manufacturers are providing free samples and posting coupons on their Web sites.

Still, specialists worry that some patients will try to save money with a decades-old nonprescription inhaler that contains a different drug, epinephrine, best known by the brand name Primatene Mist — inhalers that also contain ozone-harming CFCs. National asthma guidelines argue against such self-treatment as too risky and less effective than albuterol. The government will allow sale of those over-the-counter inhalers until December 2011 as manufacturers reformulate.

Leo has another concern: Only one of the new inhalers counts doses used. He's monitoring emergency-room statistics to see if cost-conscious patients trying to squeeze out last drops wind up using empty inhalers.

What do patients need to know as they switch?

• Expect a softer puff instead of the CFC version's cold blast of air in the back of the throat.

"They are getting their medicine," says Dr. David Rosenstreich of New York's Montefiore Medical Center. "They have to get used to it and be aware that it's working."

• The new inhalers clog more often because HFA makes the drug stickier. Clean the hole weekly, following the instructions unique to each brand.

• Never get the whole device wet.

The FDA says there's plenty of supply; it gave manufacturers several years to ramp up before the ban.

But don't wait until the last minute. When Eric Stoermer of Ann Arbor, Mich., made the switch in August, he waited a week for a new inhaler for his 11-year-old son Ethan. Their drugstore was temporarily out of stock.

"I ended up having to hunt around on an emergency basis," Stoermer says. "This is a bad thing to run out of."