Green’s Dictionary of Slang

(US) a tramp, a street person.

1991		B. McCarthy Vice Cop 134: He was sharing his space that evening with two mangy dogs, several cats, a family of long-tailed rats, and several winos and vent-men.
2000		Princeton U. Band ‘Halftime Shows’ PENN 3 Nov. 1984 🌐 Oscar, evicted from his trash can, has become a vent-man in South Philly.