HARTFORD, Conn. — As the Navy prepared to roll out cotton, flame-resistant coveralls for submarine sailors it needed first to assess a possible threat: There was concern the boats’ ventilation systems could be clogged by lint.

After testing them out aboard USS Montpelier, a Virginia-based attack submarine, the Navy gave the all-clear for skippers to begin handing out the new outfits, which replace the cotton-polyester coveralls sailors have been wearing during deployments.

“We did the testing and proved it had very little if any impact,” Cmdr. Tommy Crosby, a submarine force spokesman, said Thursday. “We had to make sure that any of the chemicals that were used in the coveralls, along with the lint and everything else, would not impact an enclosed system.”

The Navy began issuing the new coveralls to aviation and surface-fleet sailors early last year to help reduce the risks from fires on ships, but the submarine force held off until it could assess the impact on filters and other parts of the system that provides the crew’s air for breathing. All submarine crews now have been directed to make the switch by the end of this year.

The all-cotton coveralls, which are not to be worn on shore because they are not official uniforms, are still blue, with khaki belts for officers and chief petty officers and black belts for other enlisted sailors. Unit and flag patches are forbidden to protect against degradation of the flame-retardant properties, according to the Navy, but units can adopt leather or embroidered name tags.

USS Virginia, a submarine based in Groton, Connecticut, will be the first in the Atlantic to receive the new coveralls after USS Montpelier, said Navy Capt. Jim Lowther, the supply officer for the Atlantic submarine force.

“The sailors appreciate having coveralls that give them an extra layer of protection,” Lowther said.