The focus of the world’s dirty air tends to be what’s outside. Smog, car exhaust, and factory emissions are headline-getters, but the EPA has a growing body of research indicating that indoor air is often more polluted (read: pose a greater health risk) than outdoor air in even the densest and most industrialized of cities.

The compounding factor is that we spend most of our time indoors, essentially exposing ourselves to the sources of indoor air pollution throughout the day.

In some cases, the culprits can be undetectable, but in many cases, they key is to follow your nose — most of us know the telltale scent of a just-out-of-the-box electronic device or fresh-from-the-factory carpet or upholstered furniture. Sure, these scents are associated with the joy of new stuff, but they’re frequently related to the chemicals integral to production, chemicals that are known sources of indoor air pollution. It’s not so much that any one of these things is emitting noxious fumes; it’s more that our home is filled with various items that do.

Volatile Organic Compounds: One would be hard-pressed to find someone who doesn’t believe the fumes associated with paint, paint thinners, adhesives and plenty of other home-improvement and hobby materials are anything less than unhealthy. The source behind many of these products’ negative health effects is volatile organic compounds (VOCs, if you want to sound in-the-know), gases that are emitted directly into the air from solids and liquids.

VOCs include a large number of chemical agents, and the EPA says concentrations of VOCs are 10 times higher indoors than they are outdoors. They cause a host of breathing problems, headaches and nausea, and prolonged exposure can even lead to liver, kidney and central nervous system problems.

Although VOCs can be found in substances far removed from hobby materials, such as upholstery and dry-cleaned clothing, the main way to reduce risk is to reduce and limit exposure to standard household chemicals, always use them in a well-ventilated area (or even outside) and get rid of old paint, paint thinners and other products that are loaded with them, not to mention containers that have stored them.

Polyvinyl Chloride: This is the slightly sweet-smelling offender in many of the plastic products you bring into your home. It can be in everything from yard furniture to hoses, cable insulation and a cable box. The good news is that it breaks down quickly in the air, so open a window in your rec room and wait until the smell dissipates before planting yourself in front of that new entertainment system for a movie marathon.

Pesticides: A roach inside can certainly feel like the worst kind of indoor pollution problem, but the chemicals that ensure these buggers don’t live long once they get in cause a host of health hazards to humans, too. The EPA has found that the amount of pesticides found in homes exceeds the amount that can be explained by recent use of pesticides and surmises that additional sources include contaminated dust and dirt that makes its way indoors, stored pesticide containers and household surfaces that collect and continue to release them into the air. The organization puts it best: “It is important to remember that the ‘-cide’ in pesticides means ‘to kill.’" While it is commonly recognized that infestations cause health hazards of their own, use the killer chemicals sparingly. The EPA sponsors the National Pesticide Information Center, which outlines additional safe use practices.

Formaldehyde: This is widely recognized as the biggest offender in the VOC playground and easily warrants a novel. Sure, we can detect the telltale odor when walking into a high school bio lab on dissection days, and savvy shoppers might even recognize it when unwrapping anything from new pressboard to fresh-from-the-factory clothes. However, the trouble with formaldehyde is that it can be formed when other chemical products break down, and even after that factory smell wears off, the products that contain it are still emitting it. Couple the latter with the fact that it’s a regular guest star in building materials, and it’s possible to confuse the signs of exposure with a really bad, never-ending case of hay fever.

When buying new, it’s become easy enough to find products that have no added formaldehyde or at the very least do not use urea-formaldehyde, which is the biggest contaminator. If you believe your new carpet or drapes might be the offender (and they frequently are), wash down the fabric and let in plenty of fresh air (remember, even that smoggy city air can be cleaner), with a little time, all should be well.

Sources of indoor air pollution