No it's not the cat litter box or a garbage can that needs emptying.  That smell may be more than just a nasty odor, it might very well be downright hazardous.  In fact the EPA has determined that indoor air quality is typically "between two and five times more contaminated than outside air and in some cases, a hundred times more."  If, as a buyer or homeowner, you or any of your family members suffer from asthma or allergies then you should be extra concerned about the quality of the air inside any home you own or are considering purchasing.  Even if you or no one in your family is currently suffering from respiratory problems or allergies, you should still be concerned about future problems.

There are many common pollutants such as tobacco smoke that most of us are aware of.  But what about formaldehyde from pressed wood furniture and cabinet products or volatile organic compounds (VOCs) found in paint, wood floor finishing and adhesives? There are chemicals in household cleaning products and pesticides that can trigger asthma and allergies when kept in close proximity to living space and when the ventilation is less than optimal.  Have you heard about the Katrina victims living in FEMA trailers where the formaldehyde began to make people sick after a few months and FEMA initially denied there was a problem?

Mold can grow behind walls and trigger extremely serious health problems. But the results of living with some of these contaminants my not show up for years.  Some pollutants DON'T have much of a smell and the health ramifications may not be immediately noticed.  Radon has absolutely no smell and is the second leading cause of lung cancer in the United States.

Improper ventilation is one of the main causes of indoor air quality problems.  But before you go out and buy an expensive air cleaner or try to solve the problem yourself, it's a good idea to have an indoor air quality test.  A qualified indoor air quality tester can locate the areas where the air is most polluted and/or contaminated. They can then prepare a written plan that can be used to bring the indoor air up to an acceptable quality.  The caveat is that indoor air quality testing is not standardized or regulated. So it's important to use a trusted source to find a reliable individual or company. If you live in the VA, MD, DC metro area I will be happy to refer you to a first rate tester.