Although we hear a lot about outdoor pollution, when it comes to our individual health, indoor air pollution is often more dangerous. The exterior walls of your home act like a barrier to the toxins and hold them inside where they are allowed to build up. Some of these pollutants come from the outdoor air and soil and seep through cracks in the walls and foundation. Others come through an inefficient ventilation system if you have central air conditioning. Sometimes we create the most harmful pollutants in our very homes. Your furnaces and water heaters produce Carbon Monoxide gas, an odorless and toxic chemical that silently attacks your respiratory system. Cleaning chemicals and other products we use also contribute to buildup harmful to your health.