When Boston firefighters responded to a fire on a Red Line train at the Charles/MGH station Thursday morning, they did what they normally would do. They connected a hose to a nearby fire hydrant and used one of their trucks to pump water into what is known as a standpipe. That pipe is supposed to carry the water to upper floors where firefighters could access it without having to deploy hundreds of feet of hose.

But as Boston Fire Department spokesman Brian Alkins told GBH News, “As they waited for the water, they realized they weren't getting the water, or they might have gotten only some of the water. It wasn’t enough pressure in the water because of the crack or the malfunction of the pipe.”

So, instead of being carried up to the second floor where the smoking train was, the water leaked out and flooded the first floor. That’s when firefighters grabbed extinguishers and cans of water to carry them upstairs to fight the fire.

“It slowed us down a little bit because obviously we were expecting the water to come out of there, but it didn't deter us from putting the fire out,” Atkins said.

Fortunately, the fire was mostly a smoky affair and was quickly extinguished once firefighters arrived.

The T said that an AC condenser underneath a Red Line car malfunctioned and overheated. All passengers were able to evacuate safely without injury. But the incident disrupted the morning commute for two hours until the train was removed.

It’s the latest safety problem — even the latest fire — to plague the T, with a metal box falling on a woman standing on the Harvard station platform earlier this year and a rider who was dragged to his death last spring.

Milosh T. Puchovsky, a professor in the department of fire protection engineering at the Worcester Polytechnic Institute, told GBH News that frequent inspections are essential.

“Once they're put in, they often sit idle,” he said. “But when you need them, then they need to work.”

When asked about the problem with the malfunctioning standpipe — which the MBTA is responsible for maintaining — spokesperson Joe Pesaturo said that the agency had complied with national guidelines that say standpipes should be checked every five years.

“The standpipe at Charles/MGH was successfully tested and inspected in 2019,” Pesaturo said. “It’s not clear at this time what caused the problem yesterday.”

Pesaturo added the T’s investigation into the standpipe will continue.

Puchovsky said that changes could have happened between 2019 and now that would have impacted the standpipe.

“It may have been tested five years ago, but I don't know if any work had been done on the system that could have affected it in some way,” he said.

Standpipes are often required by local fire codes or building codes for certain types of high-rise buildings, large structures or transportation hubs. The type of standpipe that Puchovsky believes this was — a “dry manual” standpipe — isn’t always filled with water. That type of standpipe can make it harder to detect cracks.

“That’s why there there’s a pretty rigorous inspection testing and maintenance protocol,” Puchovsky said.