Living with COPD doesn't keep Archie Copeland from being active. In fact, it's the reason he's active.

He was diagnosed nine years ago with Chronic Obstructive Pulmonary Disease (COPD), a progressive lung disease that affects an estimated 24 million people in the U.S. - 425,000 of whom are in North Carolina.

A heavy smoker for 40 years, Copeland says he hardly exercised at all.

"I walked a lot in my work, but not any formal exercising, so this was a whole new world for me," he said. "And it's become my world now."

Now, the 72-year-old walks three to four miles a day, monitoring his blood oxygen levels and carrying his portable oxygen tank along with him.

COPD is the result of long term damage, usually from smoking, to the alveoli, or air sacs and airways in the lungs. The tissue loses its shape and elasticity, making it difficult for the lungs to take in and expel air.

The disease develops slowly. Dr. James Donohue, chief of pulmonary medicine at UNC Hospitals, says that's why half of people who have COPD go undiagnosed.

"People attribute it to asthma, getting older, being more unfit, becoming more sedentary," said Donohue. "They feel they're out of shape, but in fact, if they were tested, they would find that they had this condition."

The COPD Foundation has been traveling around the country performing free lung function tests and were in the heart of tobacco country, testing at the Durham Bulls' ballpark on Monday night. In just a few minutes, a screening with a device called a spirometer can determine how well your lungs are working.

COPD used to be considered a man's disease, but it's actually more common and more deadly in women. Doctors say that's partly because more women are smoking, but also because they're less likely to be diagnosed with the disease.

"Women are much more likely to be called asthmatic," said Donohue. "There's a real gender bias. And all patients are being diagnosed at a younger age."

Donahue says new medications and early diagnosis can make living with COPD easier. To find out more about COPD and testing for the disease, visit the Learn More Breathe Better website.