According to the National Fire Protection Association, ionization alarms have a small amount of radioactive material between two electrically charged plates that ionizes the air and causes current to flow between the plates.
Ninety-six percent of the country's homes have at least one smoke alarm, according to the National Fire Protection Association.
What kind do you have?
If it's not photoelectric it's the wrong kind, says Skip Walker, a home inspector from San Bruno, Calif., with a distinct day-night mission statement.