In the case of a national emergency, such as a natural disaster, chemical plant failure, or terrorist attack, many communities rely on warning sirens for important information. Yet many victims of the tornado that recently ravaged southern Indiana say they didn't hear the warning sirens intended to alert residents of the approaching storm. From the New York Times: The authorities in both counties said their siren systems had activated a short time before the storm, once the National Weather Service alerted them to the approaching tornado. In fact, one of Vanderburgh County's 21 sirens is about half a mile from the Eastbrook Mobile Home Park, and the three-minute alarm should have been audible there about 15 minutes before the storm hit, Sherman Greer, director of emergency management there, said. "But the truth here is, there's no perfect warning system," Mr. Greer said. Marvin Heilman, the Warrick County sheriff, said that county's sirens were "very audible," but conceded that even he did not hear the one a mile from his house that night. "It's something I know we'll look at," Sheriff Heilman said. The issue has arisen elsewhere before. Such siren systems are common in many local communities, and in states like Tennessee and Iowa, some people have raised questions about their usefulness. Besides, some residents here said, even those who heard the sirens were not always sure what to do next. 22 people died as a result of the tornado, most of them having never left their homes. National security infrastructure failures have been making headlines ever since Hurricane Katrina. And this example only further underscores how woefully unprepared we are to manage a large-scale disaster of any type.