BAY CITY — Sirens rang and lights flashed at the new Dow Bay Area Family Y at 9:20 a.m. today when the fire alarm was triggered. Maintenance crew members conducting routine clean up were clearing off fire alarm sensors in the basement of the new Y, 225 Washington Ave., when settling dust tripped the alarm. The alarm was quickly shut off and no evacuation took place, although it unsettled a line of members waiting to check in at the front desk. "Hey, these things happen," said John Rooy, membership director. Rooy said the facility is adjusting the sensitivity level of equipment to avoid further false alarms.