City Fire Department officials report that the department has experienced a large increase in carbon monoxide alarm calls lately. Lt. John Magnus of the department's Fire Prevention Bureau advises residents that most carbon monoxide alarms are only designed for seven to 10 years use. There is a chirp that sounds to alert residents when the unit reaches the end of its recommended service life; this chirp will sound every 30 seconds. Magnus said there are things homeowners and building residents can do to help reduce the amount of Fire Department calls related to CO alarms: 1. Check the manufactured date on alarms. If the date is older than March 2011, it is time to replace the alarm. 2. Replace the unit's battery every six months. Some alarms have a 10-year internal battery, so fire officials advise to check the alarm's instructions.