We feel safe in our homes, but that can be a false sense of security. The threat I'm talking about is something we can't see: indoor air pollution. The air in our homes and workplaces can be more polluted than outdoor air in the most industrialized cities, according to the Environmental Protection Agency. The EPA says the problem is compounded by the fact that Americans spend 90 percent of their time indoors. Many different things can cause indoor air pollution, and they have a cumulative effect on our health.

Let's look at one of those possible sources: our furnishings. Yes, your new carpet or cabinet could be subtly poisoning you with chemicals such as benzene, ethylene glycol or formaldehyde. It's called "off-gassing." Four of the top 10 chemicals emitted from furnishings are considered "acute" hazards, or irritants. "Poor indoor air quality can cause or contribute to the development of infections, lung cancer and chronic lung diseases such as asthma," according to the American Lung Association.

How do researchers know that some furnishings emit harmful gaseous chemicals? Greenguard, a division of UL Environment, has developed a way of testing furniture to find out. In a ­generic-looking office park outside Atlanta, researchers heft furniture into giant, airtight chambers. The chambers are made of stainless steel and glass — two materials that don't interfere with the testing because they do not off-gas. A piece of furniture sits inside the chamber for as long as a week while small tubes measure all of the chemicals coming off it.

When I was at "Good Morning America," I asked Greenguard to test furniture for a baby's nursery for a story. The rocker we tested put off seven times as much formaldehyde as the state of California considers safe. The paint contained five times the amount of chemical gases as the recommended limit. And more than 100 chemicals wafted from the crib mattress — some of them alcohols and industrial solvents.

Greenguard developed the testing method so manufacturers who wanted to sell low-emission furniture could prove their products were healthier. UL awards its Greenguard certification to furniture that emits low or no levels of hazardous chemicals. "Many manufacturers are testing their products to determine the amount of emitted volatile organic compounds," said Scott Laughlin of UL Environment. "In some cases, they may choose to reformulate their products to reduce chemical emissions."

Manufacturers don't have to state what chemicals they use in their furnishings. The EPA singles out engineered wood — otherwise known as particleboard — as being particularly prone to emitting formaldehyde, a probable carcinogen. UL Environment adds that products that are applied wet, such as glues and paints, often off-gas while they are curing. Sometimes a strong industrial odor is a good hint that a piece of furniture is emitting chemicals. If you develop a headache while inside a building where paints, stains or glues are being used, that's another clue. But it's hard for consumers to know for sure whether harmful chemicals are present.

However, it is possible to know whether harmful chemicals are not present, because more and more furnishings are being certified as having low emissions. Here are certifications you can look for and other steps you can take to reduce your exposure to indoor air pollution from your furnishings:

1. Check certifications. Look for an indoor-air-quality certification, such as the one offered by Greenguard. Another firm that certifies low-emission furniture is SCS Global Services.

2. Air out. Unwrap new furniture outdoors and let it sit for at least a week to air out. You can also unwrap traditional dry-cleaning outdoors or in a detached garage before taking it inside. Open doors and windows to get fresh air into your house as often as possible, even when you are not doing a home improvement project.

3. Paint first. If you're renovating your house, paint it and air it out before installing carpeting and curtains, because they can absorb chemical fumes from the paint. Also paint in the spring or fall when it's most comfortable to leave doors and windows open for air circulation.

4. Buy used. Off-gassing diminishes over time, so buying older furniture can be better. Just be sure the products you buy meet current safety standards, and avoid painted furniture made before 1978, the year lead paint was banned.

5. Avoid particleboard. This material is also called pressed wood, engineered wood and MDF. The glues used to hold the material together often contain harmful chemicals such as formaldehyde. Alternatively, look for certified particleboard products. "Manufacturers who use engineered wood often encapsulate the engineered wood with laminates, sealants or finishes to reduce emissions," Laughlin of UL said.

6. Choose unscented. Many products come in scented or unscented versions. The unscented ones should contain fewer chemicals.

7. Beyond furnishings. Other products frequently used in homes can also off-gas and cause indoor air pollution. Consider the potential pollution when you bring new flooring, paint, adhesives, electronics, gypsum board or insulation into your home.