A healthy home should generally have its air exchanged about three times per hour in living areas (or roughly about 15 cubic feet per minute per person). Fresh air is commonly brought in through natural, whole house or spot ventilation:

• Natural ventilation - This is the most common method of older home ventilation using windows, cracks and doors. When properly designed and controlled, this strategy is probably the best, cheapest and most pleasant way to bring in fresh air if you live in moderate climates. However, many homes fall into two categories: the "over-tight" home with inadequate ventilation, or the very drafty older home with too much leakage and high energy costs.
• Whole house ventilation - Whole house systems use ducts and fans to exchange air with the outside. A properly sized whole house system removes pollutants and provides the right amount of air without poorly affecting indoor air quality, building structure or energy bills.
• Spot ventilation - This method quickly removes pollutants, moisture, and odors through local exhaust fans such as the kitchen hood, or bathroom fan. Include spot ventilation with other types of ventilation.