Urban blight isn’t just a matter of widespread poverty, deteriorating housing, dysfunctional schools and street crime. At a certain point in a city’s decline its financial resources are so diminished that life-or-death services like policing and firefighting have to be cut back at the expense of public safety. “Burn: One Year on the Front Lines of the Battle to Save Detroit” is a compelling study of Engine Company 50, a firehouse on the east side of Detroit doing the best it can under dire circumstances.

The documentary, directed by Tom Putnam and Brenna Sanchez, is a group portrait of the company’s firefighters, who labor valiantly under increasingly stressful conditions. These men (there are no women in sight) constitute a hearty, tightly bonded brotherhood. They love their work, despite its obvious perils and low pay. A starting firefighter in Detroit, we learn, earns only $30,000 a year. There have been no raises for 10 years. Most members of the brigade have to supplement their incomes with second jobs.

Because there is almost no money for basic repairs, Company 50 struggles to make do with damaged equipment whose parts are sometimes held together by duct tape. A new fire engine would cost upward of $700,000.

As the city’s population declined to about 700,000 today from 1.85 million in 1950, abandoned houses, some of which have been taken over by squatters, serve as targets for arsonists who, according to one talking head, set fires for three reasons: “profit, revenge and kicks.” The city has 80,000 vacant structures, of which only 3,000 are torn down each year. The city’s average of 30 fires a day is one of the highest rates in the nation. The movie includes several scenes of infernos being battled inside buildings on the verge of collapse and filmed by cameras attached to the firefighters’ helmets.