The call to Bay Area firefighters came Wednesday morning.
Someone reported hearing a faint moaning, a cry for help coming from a vacant Chinese restaurant in a San Lorenzo strip mall.
When Alameda County firefighters arrived, the moaning grew louder. It was coming from inside the kitchen, above the stove. There, inside a tight metal grease vent that led to the roof, they found the source of distress.
Firefighters cut away sheet metal and found a man covered in grease and soot.
The man, whom authorities have not identified, told firefighters he had been stuck in the slick vent for two days.
It is unclear whether he was trying to break into the building, but he was arrested on suspicion of trespassing, said Alameda County Sheriff's Office spokesman Sgt. Ray Kelly.
The man was in good spirits despite his situation, Kelly said.
Temperatures in the area dipped into the 40s on Tuesday night, according to the National Weather Service.