Rita Davis is one of around 25 million Americans suffering from asthma. She's had it since childhood and finally got a portable oxygen tank a year ago.

"It doesn't feel too good. You can hardly breathe," says Davis. "Most of the time I stay inside because I can hardly handle the outside."

Especially on a 90-degree hazy day like Friday when she only goes outside if necessary, like to see her doctor. Davis cringed a bit when she heard it would be a "Code Orange" day for bad air quality.

"You have tightness in the chest. You cough a lot," adds Davis. More than on an average day.

The Environmental Protection Agency has a scale for air quality, ranging from Good to Hazardous. Orange is near the middle as Unhealthy.

Dr. Todd Levin at the Chattanooga Allergy Clinic says people with heart or lung conditions should stay indoors as much as possible on Code Orange days. Dust, dirt, and other pollutants become suspended in the lower atmosphere and make respiratory symptoms worse.

"Right now the biggest thing is ozone, which is basically an oxygen molecule that's bound to two other oxygen molecules," explains Levin. "It's very irritating to the respiratory tract."

It's a chemical reaction resulting from intense ultra-violet sunlight interacting with oxygen, which is why bad air quality typically occurs on hot days.

If people like Davis exert themselves too much outside on these types of days, it could be harder to bounce back from aggravated symptoms. It might also take longer to respond to recovery medications.

"It's not going to be deadly to walk and get your mail, but you shouldn't take a jog around the neighborhood during peak heating of the day," adds Levin.

He even urges people who don't have respiratory problems not to overdo it outside, or just stay inside, if the air quality is worse than Code Orange.

Davis just deals with life day by day.

"One day at a time. But I thank God for it. It could have been worse," says Davis.

A Code Orange is in effect again for the Chattanooga area Saturday, June 11.

For more information about air quality alerts, visit the Air Pollution Control Bureau web site here and go to Air Quality Information at the top.