Normally at this time of year people close their windows up tight to keep warm air in and cold air out. People who work in offices, stores and schools do the same thing. But when windows are tightly closed, a lot of other things may be trapped inside with the warmth--including pollution.

"Indoor air pollutants like pet dander, household dust mites, and tobacco and cooking smoke can cause itchy eyes, sneezing and runny nose," says Linda Ford, president of the American Lung Association (ALA).

Those things would be bad enough, but the problems don't end there.

Air pollution is a factor in illnesses such as respiratory tract infections, asthma and even lung cancer, according to the ALA, which also noted that poor indoor air quality can trigger headaches, fatigue and nausea. Still, 85 percent of Americans don't realize that the air in their homes may be a health hazard, according to an ALA survey released last year.

Your home's heating system can be a major source of indoor air pollution, as can other home appliances that use gas, oil or wood for fuel. Many of these produce carbon monoxide, an odorless, colorless gas that is highly poisonous. If you breathe in too much carbon monoxide, it can make you dizzy and confused, give you a terrible headache and make you feel sick to your stomach. At high levels, carbon monoxide poisoning can kill.

Not all indoor air pollution comes from machines. Natural sources include mold, bacteria, dust mites and animal dander, tiny particles from the skin, hair or feathers of household pets.

Another natural pollutant, radon, can get into your home from below. An invisible gas that is known to contribute to lung cancer, radon seeps into houses through cracks in foundation floors and walls or through drains and other openings. The ALA estimates that one of every 15 homes in the United States has radon levels too high to be considered safe. It's important to find out if your house has radon in it and to take steps to keep it out.

Of course, one of the most damaging forms of indoor air pollution is cigarette smoke--whether you're the smoker or not. Secondhand smoke, also known as environmental tobacco smoke, contains about 4,000 chemicals, including 200 known poisons. It also contains 43 substances that can cause cancer.

All this is pretty scary stuff. But there are things you and your family can do to improve the air quality in your home. The ALA says it's important to control the source of natural pollutants in the home as much as possible. This means removing as many asthma triggers as you can. Keep rooms vacuumed and dusted. Wash bedclothes in hot water to kill dust mites, microscopic animals that are a common link to allergies. Don't let pets sleep in your room. Clean up sources of mold or mildew in basements or bathrooms.

To keep fresh air moving through your house, you need to ventilate it, even when it's cold outside. Keep windows open as often as possible to allow air to circulate.

Your family should check your home for radon if you haven't already. You can get a kit at a hardware store. While you're there, pick up some carbon monoxide detectors. Like the smoke detectors you should have in your house, these could save your life someday.

Your family may also want to consider banning indoor cigarette smoking, as the operators of many public buildings have done. Refusing to let anyone smoke in your home may be the most important pollution prevention tip your family can take, and your lungs will thank you for it.

Tips for Parents

Do you smoke in your house? Here are some compelling reasons not to: Exposure to secondhand smoke has been linked to bronchitis and pneumonia, upper respiratory tract irritation, reduced lung function and increased severity of asthma symptoms in children. Environmental tobacco smoke (ETS) is also associated with middle ear infections, slower growth rates, and colds and sore throats. Children's exposure to ETS is responsible for:

* 7 percent of ear infections.

* 11 percent of asthma cases.

* 13 percent of physician visits for cough.

* 16 percent of all lung infections in children under 5.

To learn more, contact the American Lung Association at 1-800-LUNG-USA or visit the group's Web site at www.lungusa.org.

For You to Do

Smoking is on the increase among U.S. teens, according to the American Heart Association. An estimated 4.1 million U.S. adolescents ages 12 to 17 are smokers. In addition, "each day more than 6,000 young people try a cigarette for the first time, and more than 3,000 become daily smokers," said Lynn Smaha, president of the Heart Association. If you have experimented with smoking, make a late New Year's resolution today to stop for good. If you are a regular smoker, decide today to tell someone about it and get help quitting. If you have never smoked, make a resolution today to keep it that way--forever.