ASHRAE Standard 62.2, "Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings," recommends that homes receive a minimum of 1 cfm per 100 square feet of floor space, plus 7.5 cfm per person. While the ventilation rates really depend on the sources of contaminants in the home, the typical range for a home is between 30 cfm and 80 cfm.
In this age of tightly built houses, it is likely that many homes do not receive the proper amount of ventilation, even if homeowners regularly use their bathroom or kitchen fans.