BALTIMORE (WJZ) — The union representing Baltimore City’s firefighters said a shortage of medics means firefighters with proper training are being shifted to fill vacant medic positions during critical times — and the department is idling some fire engines because of it.

We’re using fire suppression to backfill and cover our EMS staff,” Richard “Dickie” Altieri, the president of Local 734, said. “They’re basically taking a fire engine and shutting it down for the day. It’s basically a rolling brownout.“

READ MORE: Baltimore County Officer Opened Fire On Driver Trying To Flee Traffic Stop: Police

Altieri said anywhere from one to six engines are placed out of service depending on the need for medics.

“It’s not that you can just say we’re going to be short today,“ Altieri said.

Altieri estimates roughly 20 percent of shifts are covered using overtime.

The fire department has already surpassed its overtime budget of more than $11 million with several months left to go in the fiscal year.

A department spokeswoman could not say the exact number of shifts covered with overtime, but said there are no safety risks to the public.

“Quite frankly it’s been an issue we’ve been dealing with for over a decade,“ department spokeswoman Blair Adams told WJZ.

READ MORE: No. 17 UConn Holds Off Maryland-Eastern Shore 72-63

“We haven’t had any issues where members are fatigued,” she said.

The department was roughly $8 million above its overtime budget the prior fiscal year and some members of the city council have been holding hearings to keep tabs on the issue.

“The Administration needs to go to City Hall and to the mayor and say, ‘This is what we need to run effectively.’” Altieri said.

He said there is a new recruiting class graduating later this year but the shortages are likely to continue.

The department faces competition from surrounding communities and increasing demand for paramedics with the opioid crisis hitting Maryland hard.

“Our call volume and run volume continually goes up especially on the EMS side of it,“ Altieri said.

Adams noted, “We’re one of the biggest EMS systems in the country.”

MORE NEWS: Shootout Between Cars Speeding In Hampden Rattles Otherwise Quiet Neighborhood

Follow @CBSBaltimore on Twitter and like WJZ-TV | CBS Baltimore on Facebook