 We're using predictive analytics. Fire Chief Tiffany Green says they know when crews are busier. We're putting peak units in certain areas. We're putting a peak unit in Greenbelt, for example, because we know during a certain time call, there's going to be more EMS calls, and we want to have an EMS unit available to run those calls. John Doehm in WTOP News. Prince George's County officials say they're currently operating at 251 career firefighters short of a full staff.