By R.E. Blake Evans Six years ago, architect Mark Humphreys specified carbon monoxide detectors for multifamily homes with attached garages that he was designing. Though not required, "I felt there could be a danger if someone left their car running in a garage and, as a result, it killed someone inside," says Humphreys, principal of Humphreys and Partners Architects in Dallas. His concerns proved prophetic. This past August a resident did just that in Columbia, S.C. Early one morning, four carbon monoxide detectors sounded alarms throughout the building, waking residents and leading to an immediate evacuation. The local fire department confirmed that multiple people would have died if it had not been for the detectors.