By about 5 p.m., on a fall evening in late November, Lt. Kevin Wittmer and his crew have already responded to 10 emergency calls. A few more will come in before 8 p.m. None of them involve fire.

During the lull in the rush, Wittmer, a professional firefighter and medic at the Prince George’s County District Heights fire station, takes a swig out of a water bottle. He still has a majority of the shift to finish before he can drive home to the Eastern Shore, where he will spend the next three days off the clock. The county’s firefighters typically work about twice a week, 24 hours a shift.

But lately, many have been working longer hours.

The central Maryland fire department, like others around the state, is experiencing unprecedented strain. The force has shrunk to fewer than 1,000 uniformed members spread out across 45 stations, leaving about 80 vacant, budgeted positions left to fill.