Improving indoor air quality can be quick and easy—87% of the families visited by Gagney’s volunteers make at least one change to freshen their air. So we asked her, and other health researchers and housing experts, to reveal common mistakes you’re probably making—plus the solutions that help you breathe easy.

Mistake: You clean your clothes dryer’s lint trap…but ignore the exhaust pipe

Eliminating buildup in the filter solves only half the problem: If the exhaust pipe is clogged, lint can escape through cracks, says contractor Tim Carter of AsktheBuilder.com.  Fix it: Clean the pipe every 3 to 6 months. Snake a round brush with long, flexible piping (about $20 at hardware stores) into the tube to pull out lint clinging to the sides. If you can’t get all the way through from one end, you may need to pull sections of the pipe apart–or hire a professional duct cleaner. Always vent your dryer to an open outdoor area: “Moisture spilling into an attic or under a dark porch is the perfect invitation for mold,” says Carter.  Ditch It: Dryer sheets Most fabric softeners are full of phthalates, chloroform, camphor, and other chemicals that can damage the respiratory, nervous, and reproductive systems, according to the EPA. Their fumes are released through a dryer’s vent—and because the substances on the sheets aren’t rinsed out as with the liquid kind, clothes stay coated with the toxins.  

Mistake : You run a bathroom fan…only when you shower

Condensation is the biggest problem in household bathrooms, and mold can flourish in the shower, between tiles, and behind the toilet. Your exhaust fan should send moisture outside during and after a hot shower.  Fix it: Add a timer. Got a fan? Great. Now connect it to a 30-minute wind-up switch that you can crank as you enter and leave the steamy bathroom. If you forget about it or leave for work, it will run its course and shut off automatically.  Install it: A fan in the kitchen Excess humidity helps dust mites thrive, so keep air moving whenever your stove, microwave, or dishwasher is producing steam. An exhaust fan above the kitchen range works best. If that’s not doable, position a box fan in your window to pull hot air outside.  

[pagebreak]Mistake: You run an air purifier…without a HEPA filter

The wrong machine could actually harm your lungs: In several University of California, Irvine, studies, ozone-generating air purifiers (marketed to reduce pollen) were found to emit dangerous levels of the gas—which is great for the upper atmosphere, but on the ground causes shortness of breath and can aggravate asthma. And ionic air purifiers, which emit only tiny amounts of ozone, can also make the air worse when used along with lemon-scented household cleaning products that contain limonene.  Fix it: Buy a HEPA model. This kind of filter has been shown to remove 99% of airborne particles without producing harmful by-products. We like the new Honeywell HEPAClean 3-in-1 Air Purifier ($250; amazon.com), which also has a germ-fighting UV light and an odor neutralizer. HEPA purifiers in the bedroom and living areas may improve breathing for anyone with asthma or allergies to dust, mold, or pets, says Hugh Windom, MD, an associate clinical professor of allergy and immunology at the University of South Florida. Skip it: Plug-in or desktop models “They’re not powerful enough to make a difference even in the smallest room,” says Windom. When buying larger units, note the square footage a purifier can treat, listed on the package.  

Mistake: You change your vacuum bag…when it feels full

Vacuuming once a week will keep dust from accumulating deep in carpets, but the bag will fill up fast. A full bag reduces efficiency and can even spew dust back into the air.  Fix it: Toss bags when they’re half full. It’ll be a little more expensive, but you’ll deposit less dust back into the air—which means the vacuum will have less to pick up from now on.  Buy it: The Hoover Windtunnel vacuum ($140; hoover.com) Its True HEPA filter traps allergens, and its green light/red light “Dirt Finder” technology tells you when a surface is really clean. (A tiny microphone listens for dirt particles rattling through its tube.) “People underestimate how long they need to vacuum,” says Gagney. An initial deep clean can take 45 minutes on high-traffic carpet; following sessions may still require several strokes back and forth. As for bagless models, don’t bother: “When you empty those canisters,” Gagney says, “you’re less than 2 feet away from all that dirt and breathing it in.” [pagebreak]  

Mistake: You warm up your car…in the garage

Even with the garage door open, it’s dangerous to run an automobile in a garage—especially one attached to the house. “When you step from your house into your garage, a wall of cold air rushes through the door,” says Gagney. That’s when deadly carbon monoxide—or vapors from open paints, solvents, or pesticides—can make their way in.  Fix it: Reduce fumes and seal entrances. Install a self-closing door (or put springs on your existing one) so it’s never left open by mistake. And make sure all doorways—and any cracks leading to the first floor or to a room above the garage—are airtight. Most importantly, never run the car in the garage.  Check it: Your furnace Faulty heating systems are the leading cause of carbon monoxide poisoning in the home, so have yours examined professionally before turning it on each year, especially if it’s more than 5 years old.  

Mistake: Your home’s been cleared for lead…but not radon

The dangers of lead poisoning are well-known, and lead paint has been phased out of housing construction nationwide. But few states regulate another contaminant—the leading cause of lung cancer after cigarette smoking: radon. Nearly 1 out of 15 homes in the United States is estimated to have elevated levels of the radioactive gas that can seep from soil into a home’s foundation. (Find more details about your county at epa.gov/radon/zonemap.html.)  Fix it: Test your levels. Low-cost kits that measure radon for about a week are available at hardware stores or by calling (800) 767-7236. Keep windows closed and place the kit at your home’s lowest surface for an accurate reading. If your levels are 4 pCi/L (picocuries per liter of air) or higher, test again.  Schedule it: An appointment with a specialist If results are the same, call your state radon office (find yours via epa.gov/radon/radontest.html) and arrange for follow-up tests. “You may need to install a ventilation system,” says R. William Field, PhD, professor of occupational and environmental health at the University of Iowa. “Or it could be as simple as sealing cracks or areas where pipes enter the home.” [pagebreak] Check these items at the door to help keep your home’s air clean:  Cigarettes It’s not just smoke that dirties the air—it’s the particles on smokers’ clothing, too. If a guest must step outside for a cigarette, ask her to wear a “smoking jacket” that stays out in a breezeway or garage.  Dry cleaning Traditional cleaners use perchloroethylene, a chemical shown to cause cancer in animals. Look for a shop that uses silicone or carbon dioxide instead (some are listed at greenearth cleaning.com and findco2.com)—and air your unbagged garments outside for 3 hours before putting them in your closet.  Shoes Outside, the sun and the elements break down pesticides; when they’re tracked indoors, they stick around in your carpet and make their way into the air. Keep a shoe rack and basket of slippers by the door for quick changes.  Firewood When burned, even untreated logs release harmful gases and tiny particles that get into the lungs and bloodstream. Use your fireplace sparingly with artificial timber—like Duraflame’s All Natural Firelog—or, better yet, switch to gas.