Not all cleaning is smart. Air ducts need cleaning only in limited circumstances-when there's visible mold, pests, or dust clogging them. Still, 49 percent of survey respondents clean their ducts at least once a year.

What you can do:

  • Every season, check gutters, leaders, and downspouts for proper pitch, clogs, and broken fasteners or connections.
  • Make sure that gutter pipes extend at least 5 feet from the house and that the soil around the foundation slopes away from the house.
  • Avoid mold test kits; we've found them to be unreliable.
  • Treat small areas of mold with a mixture of 1 part chlorine bleach and 16 parts water. Wear goggles, an N-95 respirator, and heavy-duty gloves. Make sure to ventilate the room when you're working.

Air fresheners, candles and incense:
Behind the soothing fragrances of air fresheners, candles, and incense are volatile organic compounds. Air fresheners can also contain phthalates, which are linked to cancer and reproductive problems.

"A few manufacturers changed their products after our 2007 report found phthalates in 12 of 14 air fresheners we tested," said Gina Solomon, M.D., a senior scientist at the National Resources Defense Council.   "That's good, because companies are reformulating to make their products safer, but it's also bad because it's hard to know what's currently in any given product."

Scented candles and incense also release soot and particles into the air, which can trigger asthma attacks and allergic reactions.

What you can do

  • If you or someone in your household has serious allergies or asthma, avoid air fresheners, candles, and incense.
  • If pollen or related allergies keep you from opening windows, run your air conditioner or forced-air cooling system with a clean filter. Or consider a filter-based air purifier.