Fire crews say a faulty furnace is the source of a significant carbon monoxide leak in a Falls Church apartment building that has forced several residents from their homes and sent three patients to the hospital. According to Dan Schmidt, spokesman for Fairfax County Fire and Rescue, medics were called to the 3-story garden apartment building in the 3600 block of Malibu Circle around 2:30 Wednesday morning. Once on scene paramedics recognized patients with symptoms associated with carbon monoxide poisoning, prompting fire crews to check CO levels. Schmidt says readings indicated elevated carbon monoxide levels present in the building and called for an immediate evacuation of all 11 units. Three people have been taken to a local hospital for treatment. Schmidt says the victims were conscious when they were transported, however their exposure is considered potentially life-threatening.