It's estimated that the average North American spends 87 percent of their time indoors; 93 percent if you include time spent in cars. And unsurprisingly, indoor time is at its peak during cold winter months.
With the relatively high price of energy these days, people are actively working to keep the cold air out and energy costs down. Buildings are becoming more airtight, with better insulation and higher efficiency windows and doors. Unfortunately, these highly insulated homes decrease the overall flow of fresh air in a building, and they may be causing us to breath dirty, recirculated air.
One of the best ways to get a sense of your indoor air quality is by paying attention to whether you notice a distinctive scent upon entry. Do you smell cooking odors, garbage, or must? If your home doesn't smell fresh and natural, it may be a sign that you have inadequate ventilation.