CARLE PLACE - A man who walked into a doughnut shop for a cup of coffee walked out a hero after he averted a potentially life-threatening leak.

Nassau County AMT Joseph Biundo says he stopped at the Dunkin' Donuts on Glen Cove Road in Carle Place on Friday morning. He was wearing a personal monoxide detector, and to his surprise, it went off.

Biundo says he exited the store and his device went back to zero, but when we went back inside, it detected the presence of the odorless gas at 35 parts per million.

"I asked to go in the back, where the ovens were, and back there it shot up to over 80 parts per million," Biundo says.

The AMT quickly called the fire department and it was determined that an oven exhaust fan wasn't working properly. Biundo says if someone had been exposed to those levels of carbon monoxide for several hours, it could have been deadly.

Biundo is not required to carry the CO meter with him, but he purchased one for himself for $200 after the fatal carbon monoxide poisoning incident at a Legal Sea Food restaurant in February.

Nassau County recently passed a law that would require CO detectors in all commercial buildings by Jan. 1, 2015.