Many people are all too familiar with asthma and how scary an asthma attack can feel - about 25 million Americans have it.

"Asthma is a chronic lung disease that causes airways to become inflamed, narrow and swell, as well as produce excess mucus, all of which makes breathing difficult," said Geisinger emergency physician Ronald S. Strony, M.D.

When you have an asthma attack, your chest feels tight, you may cough or wheeze, and feel like you just can't seem to catch your breath.

There's no cure for asthma and, in some cases, it can be severe enough to keep kids out of school, sideline them from physical activity, and cause adults to miss days of work.

"If you have asthma, you have to be careful to avoid anything that triggers your asthma attacks, especially if you have a severe case of the disease," Dr. Strony said.

Preventing asthma attacks could be as simple as avoiding tobacco smoke and dust. However, for some asthma sufferers, it's not as easy - their triggers could simply be in the air they need to breathe.

"Air quality is a term used to describe the state of the air around us, which is particularly important for asthmatics who can suffer greatly from poor air quality," Dr. Strony said. "Poor air quality refers to ground-level ozone and other air pollutants that can trigger worsening symptoms and asthma flare-ups."

Good air quality means that the air is clean, clear and unpolluted. When the air quality is poor, pollutants reach high enough concentrations to negatively impact your health, especially if you have asthma.

Just like the weather changes each day, so does the Air Quality Index calculated by the U.S. Environmental Protection Agency (EPA). The Air Quality Index consists of four major air pollutants: ground level ozone, particle pollution, carbon monoxide and sulfur dioxide.

"The pollutants that make up the Air Quality Index have the ability to irritate anyone's lungs at high levels. So when an asthmatic is outside when the Air Quality Index is high, they're even more susceptible to suffering lung and airway inflammation," Dr. Strony said.

With allergy season starting and hot summer weather right around the corner, it's important for individuals with asthma to become aware of what the different Air Quality Index categories mean and when to stay inside.

"Being exposed to poor air quality can result in more doses of asthma drugs, emergency treatment, reduced lung function, and make it more difficult to breathe deeply. Both long term and short-term exposure to poor air quality can cause more health problems and worsen your asthma," Dr. Strony said.

Each category of Air Quality Index has an assigned color to make it easy to determine whether the air pollution is reaching unhealthy levels. Green is the best - it means the air quality is good and air pollution poses little to no risk that day. Code yellow denotes there's only moderate health concerns.

"When the Air Quality Index reaches code orange, that's when asthmatics should consider restricting how much time they spend outside - code orange is unhealthy for sensitive groups," Dr. Strony said.

Any levels above code orange - code red or code purple - will negatively impact everyone's health, not just individuals with asthma.

"If you have asthma and the Air Quality Index is forecast to rise to code orange, you should consider limiting any prolonged outdoor activities," Dr. Strony said.